Last updated: 12-08-2018
Journey to the West depicts the monk Tripitaka as the earthly reincarnation of Master Golden Cicada (Jinchan zi, 金蟬子), the Buddha’s fictional second disciple. The monk’s background is first hinted at in chapter 8 when, after receiving instructions to find a scripture pilgrim, the Bodhisattva Guanyin exclaims, “Lo, this one journey will result in a Buddha son returning to keep his primal vow. The Gold Cicada Elder will clasp the candana” (Wu & Yu, 2012, vol. I, p. 207). Chapter 12 contains a poem introducing Tripitaka as the chosen scripture pilgrim and reveals his heavenly origin. The first part reads:
Gold Cicada was his former divine name.
As heedless he was of the Buddha’s talk,
He had to suffer in this world of dust,
To fall in the net by being born a man
[…] (Wu & Yu, 2012, vol. 1, p. 275).
Details about the extent of the former celestial’s punishment is revealed throughout the book. For instance, in chapter 33 a demon explains the source of Tripitaka’s heavenly aura: “That Tang Monk is actually the incarnation of the Elder Gold Cicada, a virtuous man who has practiced austerities for ten existences” (Wu & Yu, 2012, vol. 2, p. 105). Furthermore, in chapter 100 the Buddha remarks that his former disciple was “banished to find another incarnation in the Land of the East” and that “by remaining faithful to [Buddhism], succeeded in acquiring the True Scriptures” (Wu & Yu, 2012, vol. 4, p. 381). So we learn the Golden Cicada was banished to live out ten pious lives in China until the time came for him to gain merit as the scripture pilgrim, thereby gaining reentry into paradise.
Anthony C. Yu (2008) vaguely alludes to chapter 99 explaining the source of the name Golden Cicada (p. 110). I can’t find such an overt explanation, but the chapter does mention the monk miraculously surviving drowning after being dumped into a heavenly river, along with his disciples and the hardwon scriptures, by a disgruntled turtle spirit.  Guanyin exclaims: “Ah! It was fortunate that the Tang Monk had cast off his mortal frame and attained the way. If he were like the person he had been before, he would have sunk straight to the bottom” (Wu & Yu, 2012, vol. 4, p. 363). The “cast[ing] off of his body” (tuotai, 脫胎) is reminiscent of the way in which the real life insect sloughs off its shell (fig. 1). If this is what Yu was referring to, I think this is but one part of the puzzle.
Fig. 1 – A newly formed cicada clinging to its shell (larger version).
I suggest the author/compiler of Journey to the West chose the imagery of the cicada for the symbolic nature of its life cycle. Hugo Munsterberg (1972) describes the insect’s role in ancient Chinese religion: “Cicadas carved in jade are frequently found in graves of the Han period [fig. 2]. Since the cicada hatches above ground, spends a long period underground, and finally emerges as if in rebirth, these burial tokens were probably intended to induce resurrection by sympathetic magic” (32). The Golden Cicada’s life follows this cycle very closely. The celestial being resides above in the Western Paradise, is banished below for an extended period of time, and is only allowed back into the celestial realms after a metamorphosis.
The lifesaving transformation previously referred to by Guanyin takes place in chapter 98 when Tripitaka and his disciples are ferried across a heavenly river in a bottomless boat on their way to the Western Paradise:
All at once they saw a corpse floating [fig. 3] … upstream, the sight of which filled the elder [Tripitaka] with terror.
“Don’t be afraid, Master,” said Pilgrim [Sun Wukong], laughing. “It’s actually you!”
“It’s you! It’s you!” said Eight Rules [Zhu Bajie] also.
Clapping his hands, Sha Monk also said, “It’s you! It’s you!”
Adding his voice to the chorus, the boatman also said, “That’s you! Congratulations! Congratulations!” Then the three disciples repeated this chanting in unison as the boat was punted across the water. In no time at all, they crossed the Divine Cloud-Transcending Ferry [Lingyun du, 凌雲渡] all safe and sound. Only then did Tripitaka turn and skip lightly onto the shore. We have here a testimonial poem, which says:
Delivered from their mortal flesh and bone,
A primal spirit of mutual love has grown.
Their work done, they become Buddhas this day,
Free of their former six-six senses sway (Wu & Yu, 2012, vol. 4, pp. 345-346). 
Here, we see Tripitaka has shed his mortal form to become a buddha just like the cicada sheds its shell to grow wings and fly. The monk has freed himself from the endless cycle of birth and death to achieve nirvana.
Fig. 3 – A woodblock print detail showing the shedding of Tripitaka’s mortal body (larger version). From Mr. Li Zhuowu’s Literary Criticism of Journey to the West (16th-c.).
It’s interesting to note that the early Ming zaju play Journey to the West (c. 15th-century) depicts Tripitaka as the reincarnation of an arhat named Pulujia (毗廬伽尊者). Dudbridge (1970) translates this as Vairocana (p. 193), which is the name of a major Buddha. This shows Tripitaka was associated with heavenly personages even before the final 1592 novel was published. Therefore, the author/compiler of the novel no doubt fashioned the tribulations of the Golden Cicada around preexisting folklore.
The 36 Stratagems (Sanshiliu ji, 三十六計, c. 5th-6th-cent.), a collection of military, political, and civil tactics, contains a plan known as “The Golden Cicada Sheds its Shell” (Jinchan tuoke, 金蟬脫殼), which entails leaving a decoy that distracts the enemy while the losing force is retreating. I’m not sure if this directly influenced the celestial’s title, but it at least shows the name was known long before Journey to the West was published.
The strategy is used by a tiger demon in chapter 20:
Whipping out the iron rod, Pilgrim [Sun Wukong] shouted, “Catch him!” Eight Rules [Zhu Bajie] at once attacked with even greater ferocity, and the monster fled in defeat. “Don’t spare him,” yelled Pilgrim. “We must catch him!” Wielding rod and rake, the two of them gave chase down the mountain. In panic, the monster resorted to the trick of the gold cicada casting its shell: he rolled on the ground and changed back into the form of a tiger. Pilgrim and Eight Rules would not let up. Closing in on the tiger, they intended to dispose of him once and for all. When the monster saw them approaching, he again stripped himself of his own hide and threw the skin over a large piece of rock, while his true form changed into a violent gust of wind heading back the way he had come. (Wu & Yu, 2012, vol. 1, p. 401). (emphasis mine)
I would like to suggest the name Golden Cicada Elder (Jīn chán zi, 金蟬子) might have been chosen to serve as a pun for “child or student of Chan” (chánzǐ, 禪子) (fig. 4). While the historical Xuanzang was the patriarch of the Yogacara school of Chinese Buddhism (Robert & David, 2013, pp. 1015-1016), the novel closely associates him with Chan:
The depiction of the novelistic Xuanzang surely and constantly associates him and his entourage with Chan. Revealing examples can readily be found in both narrative content and such titular couplets as “Tripitaka does not forget his origin; / The Four Sages test the Chan Mind” (chapter 24); “The Child’s tricky transformations confuse the Chan Mind; / Ape, Horse, Spatula, and Wood Mother-all are lost” (chapter 40); “The Chan Lord, taking food, has demonic conception; / Yellow Dame brings water to dissolve perverse pregnancy” (chapter 53); “Rescuing Tuoluo, Chan Nature is secure; / Escaping defilement, the Mind of Dao is pure” (chapter 67); “Mind Monkey envies Wood Mother; / The demon lord plots to devour Chan” (chapter 85); and “Chan, reaching Jade-Flower, convenes an assembly; / Mind Monkey, Wood, and Earth take in disciples” (chapter 88) (Wu & Yu, 2012, vol. 1, pp. 64-65).
If true, this would mean the cicada-like spiritual transformation was based around a pun.
Fig. 4 – The similarities in form and pronunciation of chanzi (larger version).
This seems like such an obvious connection that I wouldn’t be surprised if someone else beat me to the conclusion by decades or even centuries.
1) The turtle had previously helped the pilgrims cross the same river in chapter 34, and in return they agreed to ask the Buddha when the terrapin would be allowed to achieve human form (for all creatures strive for such an attainment). But Tripitaka forgot to ask the Enlightenment One while visiting the Western paradise, so the turtle dumped them into the river upon their return.
2) The six-six senses (liuliu chen, 六六塵) are “the intensified form of the six gunas, the six impure qualities engendered by the objects and organs of sense: sight, sound, smell, taste, touch and idea” (Wu & Yu, 2012, vol. 4, p. 405 n. 7)
Munsterberg, H. (1972). The arts of China. Rutland, Vt: C.E. Tuttle Co.
Wu, C., & Yu, A. C. (2012). The journey to the west: volumes 1-4. Chicago: University of Chicago Press.
Yu, A. C. (2008). Comparative journeys: Essays on literature and religion East and West. NY: Columbia University Press.