The best replacement for cocoon is chrysalis.

The best alternatives to cocoon are rated as following:
★★★★★  chrysalis
★★★  pupa
★  nested form
★  cocoon
★  sea to summit
★  nest
  footmuff
  moth cocoon

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Speaking about cocoon, one probably shouldn't forget about saxon.

Other search terms related to cocoon and their ratings are:
★★★★★ saxon
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cocoon
chrysalis
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