1955, a linguist's word, from hypo- + second element from Greek onyma "name" (from PIE root *no-men- "name"), with abstract noun ending. The relationship between two words where one may invariably be replaced by the other without changing the sense but not vice versa.

in grammar, "dependent construction" (opposed to parataxis), 1844, earlier in German; see hypo- + taxis. Related: Hypotactic.

1680s, "pledge (something) without giving up control of it; pawn; mortgage," from hypothecat-, past-participle stem of Medieval Latin hypothecare, from Late Latin hypotheca "a pledge," from Greek hypothēkē "a deposit, pledge, mortgage," from hypo- "beneath, under" (see hypo-) + tithenai "to put, to place," from reduplicated form of PIE root *dhe- "to set, put." Related: Hypothecated; hypothecating; hypothecation; hypothecary.