OE 'hærfest' meant 'autumn' — from PIE *kerp- (to pluck); it narrowed to crop-gathering when 'autumn' displaced it as the season name.
The process or period of gathering in crops; the season's yield of a natural product.
From Old English 'hærfest' (autumn, harvest season), from Proto-Germanic *harbistaz, from PIE *kerp- (to pluck, to gather, to harvest). The original meaning was 'autumn' — the harvest season — and the word meant 'autumn' in English until the 16th–17th centuries, when 'autumn' (from French) and 'fall' (from the phrase 'fall of the leaf') displaced it. 'Harvest' then narrowed to mean specifically the act of gathering crops
'Harvest,' German 'Herbst,' Latin 'carpere' (to pluck), and Greek 'karpos' (fruit) all descend from PIE *kerp- (to pluck, gather). English 'harvest' originally meant 'autumn' — the plucking season — and only shifted to mean 'crop-gathering' when 'autumn' (from French) and 'fall' (from 'fall of the leaf') took over the seasonal meaning in the 1600s. German 'Herbst' still means autumn.