late 14c., gelee, gelle, gelly, "semisolid substance from animal or vegetable material, spiced and used in cooking; chopped meat or fish served in such a jelly," from Old French gelee "a jelly," also "a frost," noun use of fem. past participle of geler "to congeal, to freeze," from Latin gelare "to freeze, congeal, stiffen," related to gelu "frost," from PIE *gela-, suffixed form of root *gel- "cold; to freeze."

By early 15c. it was used of any jellied or coagulated substance; from 16c. as "thickened juice of a fruit prepared as food."

c. 1600, transitive and intransitive, from jelly (n.). Related: Jellied; jellying.

1590s, "of the consistency of jelly;" 1895, sweetened with jelly; past-participle adjective from jelly (v.).

"assume the consistence of jelly," 1869, American English, probably a back-formation of jelly (n.). Related: Jelled; jelling. Figurative sense is first attested 1908. Middle English had gelen "congeal," but it disappeared after 15c.

also jelly-roll, "cylindrical cake containing jelly or jam," 1873, from jelly (n.) + roll (n.). As slang for "vagina; sexual intercourse" it dates from 1914 ("St. Louis Blues").

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).

"small bean-shaped sugar candy with a firm shell and a thick gel interior," 1905, from jelly (n.) + bean (n.). So called for its shape. Soon used in U.S. slang for "stupid person," probably encouraged by the slang sense of bean as "head."

Proto-Indo-European root meaning "cold; to freeze." 

It forms all or part of: chill; cold; congeal; cool; gel; gelatine; gelatinous; gelato; gelid; glace; glacial; glaciate; glaciation; glacier; glaciology; glacis; jell; jelly.

It is the hypothetical source of/evidence for its existence is provided by: Latin gelare "to freeze," gelu "frost," glacies "ice;" Old English cald "cold, cool," German kalt.

type of savory meat jelly, 1789, from French aspic "jelly" (18c.), apparently from Old French aspe "asp" (see asp). The foodstuff said to be so called from its coldness (froid comme un aspic is said by Littré to be a proverbial phrase), or the colors in the gelatin, or the shape of the mold. It also was a French word for "lavender spike" and might refer to lavender as a seasoning element in the jelly.

1713, from French gélatine (17c.) "clear jelly-like substance from animals; fish broth," from Italian gelatina, from gelata "jelly," from gelare "to jell," from Latin gelare "to freeze, congeal" (from PIE root *gel- "cold; to freeze"). With chemical suffix -ine (2). Spelling gelatin is from 1800. "The form without final -e is in scientific (or pseudo-scientific) use only ..." [Fowler].