Etymology
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jellyfish (n.)
also jelly-fish, popular name of the medusa and similar sea-creatures, 1796, from jelly (n.) + fish (n.). So called for its soft structure. Figuratively, "person of weak character," 1883. Earlier it had been used of a type of actual fish (1707).
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nematocyst (n.)

"thread cell, lasso cell," such as the stinging organs of jellyfish, 1875, from nemato- + cyst. Related: Nematocystic.

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blubber (n.)
late 14c., blober "a bubble, bubbling water; foaming waves," probably echoic of bubbling water. Original notion of "bubbling, foaming" survives in the figurative verbal meaning "to weep, cry" (c. 1400). Meaning "whale fat" first attested 1660s; earlier it was used in reference to jellyfish (c. 1600) and of whale oil (mid-15c.). Compare bubble.
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medusa (n.)

"jellyfish," 1758, as genus name, from Medusa, the name of one of the three Gorgons with snakes for hair, whose glance turned to stone whomever looked upon it (attested in English from late 14c.). Her name is from Greek Medousa, literally "guardian," fem. present participle of the verb medein "to protect, rule over" (from PIE root *med- "take appropriate measures"). The zoological name was chosen by Linnæus, suggested by the creature's long tentacles. Related: Medusoid.

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