Cyst

google

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early 18th century: from late Latin cystis, from Greek kustis ‘bladder’.

wiktionary

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From Late Latin cystis, from Ancient Greek κύστις(kústis, “anatomical sac”)

etymonline

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cyst (n.)

"bladder-like bag or vesicle in an animal body," 1713, from Modern Latin cystis (in English as a Latin word from 1540s), from Greek kystis "bladder, pouch," which is of uncertain etymology.