What's the "een" in Halloween?
Old English for "for, before, on account of," from Proto-Germanic *fura (cf. Old Saxon furi "before," Old Frisian for, Middle Dutch vore, Dutch voor "for, before;" German für "for;" Danish for "for," før "before;" Gothic faur "for," faura "before"); see fore (adv.).
Use of for and fore gradually was differentiated in Middle English. Its use alone as a conjunction (not found before 12c.) probably is a shortening of common Old English phrases such as for þon þy "therefore," literally "for the (reason) that."
prefix usually meaning "away, opposite, completely," from Old English for-, indicating loss or destruction, or completion, also used as an intensive or pejorative element, which is related to Old Norse for-, Dutch ver-, Old High German fir-, German ver-; from PIE *pr-, from root *per- (1) "forward, through" (see per). Probably originally in Germanic with a sense of "forward, forth," but with complex sense developments in the various languages. Ultimately from the same root as fore (adv.).