‘Shàng xián’ literally combines ‘shàng’ (up, upper) and ‘xián’ (string, bowstring), historically referencing the crescent shape of a bow—hence its use for the first quarter moon, when the illuminated portion appears as a thin, upward-curving crescent. In traditional Chinese lunar calendars, ‘shàng xián’ specifically denotes the period from the first quarter moon (about day 7–8 after the new moon) to just before the full moon, though it most commonly refers to the first quarter phase itself.

The term also has a mechanical meaning: ‘to wind (a clock or watch)’, derived from the action of tightening a spring ‘upward’ onto a barrel—a metaphorical extension of ‘shàng’ (to mount/apply) and ‘xián’ (spring, originally ‘bowstring’). This usage is now rare in daily speech, largely replaced by ‘shàng fā tiáo’ or simply ‘fā tiáo’, but remains recognizable in older texts or technical contexts.