"substitute," 1904, show-biz slang, from stand (v.). As a noun, it is attested from 1928.
To substitute; act as a proxy: I'll have to stand in for her and run the meeting (1904+ Show business)
[perhaps fr the use of a substitute to replace a performer during such tedious procedures as adjusting lights, arranging the stage or set, etc; perhaps also fr the earlier notion of a deputy or place-holder, literally a lieutenant, in French, ''a place-holder'']