Where does “forth” come from?

forth (Middle English) comes from Old English forþ, from Proto-Germanic furþą, from Proto-Indo-European pr̥to-.

Ancestry of “forth”, step by step

Step	Language	Word	Meaning
1	Old English	forþ	"expresses the continuation of an action"; out,...
2	Proto-Germanic	furþą	forward
3	Proto-Indo-European	pr̥to-	—

forth — Etymology, Origin & Word History | Etymology Explorer