sale n.

Middle English sale, from late Old English sala "a sale, act of selling," which according to OED probably is from a Scandinavian source such as Old Norse sala "sale," but in either case from Proto-Germanic *salo (source also of Old High German sala, Swedish salu, Danish salg), from PIE root *sal- (3) "to grasp, take."

The specific application to a public auction is by 1670s. The sense of "a selling of shop goods at lower prices than usual" is attested by 1866. To be for sale "available for purchase, intended to be sold" is by 1610s; on sale in the same sense is by 1540s; the earlier form was to sale (late 14c.). Salariat "the salaried class" is by 1918, from French. Also see sales.