Etymology
From Middle English sarse, probably from Anglo-Norman cerche, *cerce, from Late Latin *circa.
Traditionally derived from Old French saas (Late Latin *saetāceus (pannus) (“(cloth) made of bristles”)), but this does not explain the -r- or the final -e of the Middle English form; intrusive -r- before /s/ is sometimes found in Middle English, but one would expect etymological r-less forms to appear alongside such forms.