"portable screen or wall to absorb sound or reflect light," 1930, American English, Hollywood movie set slang, of unknown origin, perhaps somehow from go-between.
Entries linking to gobo
go-between n.
"one who passes between parties in a negotiation or intrigue," 1590s, from verbal phrase go between in obsolete sense "act as a mediator" (1540s), from go (v.) + between.