"of, pertaining to, or consisting of gelatin; of the nature or consistence of gelatin; resembling jelly," 1724, from gelatine + -ous; probably modeled on French gélatineux. Related: Gelatinously; gelatinousness.
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].
word-forming element making adjectives from nouns, meaning "having, full of, having to do with, doing, inclined to," from Old French -ous, -eux, from Latin -osus (compare -ose (1)). In chemistry, "having a lower valence than forms expressed in -ic."