Dutch word herfst comes from Proto-Indo-European *kerp-

Detailed word origin of herfst

Dictionary entry	Language	Definition
*kerp-	Proto-Indo-European (ine-pro)
*harbaz	Proto-Germanic (gem-pro)
*harƀustaz	Proto-Germanic (gem-pro)
*hervist	Old Dutch (odt)
herfst	Dutch (nld)	Autumn, fall.