Old English fullfyllan "fill up" (a room, a ship, etc.), "make full; take the place of (something)," from full, adj., here perhaps with a sense of "completion" + fyllan (see fill, v., which is ultimately from the same root). Used from mid-13c. in reference to prophecy (probably translating Latin implere, adimplere). From mid-13c. as "do, perform; carry out, consummate, carry into effect;" from c.1300 as "complete, finish; satiate, satisfy, gratify." Related: Fulfilled; fulfilling. Modern English combinations with full tend to have it at the end of the word (as -ful), but this is a recent development and in Old English it was more common at the start, but this word and fulsome appear to be the only survivors.