Cosecha (Spanish for “harvest”) comes from the Latin collectus, meaning, “collected.”
This makes sense: a harvest is, well, just collected.
Although the English collected is almost identical to the Latin, we can see how the Latin changed into the Spanish: the ‑ll- turned into an ‑s-, in a curious change. But — as is more common — the ‑ct- became a ‑ch- (think nocturnal/noche or octagon/ocho). Thus, the c‑ll-ct of collect maps to the c‑s-ch of cosecha.