"a bending or drooping," 1580s, in nautical use, "movement to leeward," from sag (v.). From 1727 in American English in reference to landforms having a sunken look. By 1861 in reference to droop from slackness in wires, cables, etc.
late 14c., "sheep-shearer;" early 15c., "a barber;" c. 1300 as a surname; agent noun from Middle English clippen "shorten" (see clip (v.1)). In late 18c., the word principally meant "one who cuts off the edges of coins" for the precious metal.
The type of sailing ship with sharp lines and a great spread of canvas is so called from 1823 (in Cooper's "The Pilot"), probably from clip (v.1) in sense of "to move or run rapidly." Compare early 19c. clipper "person or animal who looks capable of fast running." Perhaps it was influenced by Middle Dutch klepper "swift horse," which is echoic (Clipper appears as the name of an English race horse in 1831). The nautical sense was perhaps originally simply "fast ship," regardless of type:
Well, you know, the Go-along-Gee was one o' your flash Irish cruisers — the first o' your fir-built frigates — and a clipper she was! Give her a foot o' the sheet, and she'd go like a witch — but somehow o'nother, she'd bag on a bowline to leeward. ["Naval Sketch-Book," by "An officer of rank," London, 1826]
The early association of the ships was with Baltimore, Maryland. Clipper-ship is attested from 1850.