jellyfish

the term 'jellyfish' is a transparent english compound formed in the early 18th century. the first element, 'jelly', derives from the culinary substance known for its soft, wobbly, and translucent consistency, which serves as a vivid metaphor for the creature's gelatinous bodily structure. the second element, 'fish', employs the broad, archaic zoological sense of the old english word 'fisc', which was historically used for any aquatic animal, not just true finned fish. thus, the compound's literal logic is "a jelly-like aquatic creature," an apt description that distinguishes it from true fish while explaining its popular name. the later, figurative sense applied to a weak-willed person draws directly from the perceived limp and formless physicality of the animal.

Structure: jelly + fish jelly (from middle english 'gelly', from old french 'gelee', meaning 'frost, jelly', from latin 'gelata' meaning 'frozen, congealed', functioning as a descriptive modifier in the compound). fish (from old english 'fisc', meaning 'fish', from proto-germanic 'fiskaz', functioning as the head noun in the compound).