early 15c., from Anglo-French oster (late 13c.), Old French oster "remove, take away, take off; evict, dispel; liberate, release" (Modern French ôter), from Latin obstare "stand before, be opposite, stand opposite to, block," in Vulgar Latin, "hinder," from ob "against" (see ob-) + stare "to stand," from PIE root *sta- "to stand" (see stet). Related: Ousted; ousting.