[strip of cloth] 1590s, originally in reference to Oriental dress, "strip of silk, fine linen, or gauze wound round the head as a turban," from Arabic shash "muslin cloth." The general meaning "scarf or strip of cloth worn by men about the waist or over the shoulder" for ornament is recorded by 1680s.
framed part of a window, into which the panes are fitted, 1680s, sashes, a mangled Englishing of French châssis "frame" of a window or door (see chassis).
The word was mistaken as a plural and further mangled by loss of the -s by 1704. Sash-door, one having panes of glass to admit light, is by 1726; sash-weight, attached by cords to either side of a sash to balance it and make it easier to raise and lower, is attested by 1737.