c.1300, "booth or shed for trade or work," perhaps from Old English scoppa, a rare word of uncertain meaning, apparently related to scypen "cowshed," from Proto-Germanic *skoppan "small additional structure" (cf. Old High German scopf "building without walls, porch," German dialectal Scopf "porch, cart-shed, barn," German Schuppen "a shed"), from root *skupp-. Or the Middle English word was acquired from Old French eschoppe "booth, stall" (Modern French échoppe), which is a Germanic loan-word from the same root.
Meaning "building or room set aside for sale of merchandise" is from mid-14c. Meaning "schoolroom equipped for teaching vocational arts" is from 1914, American English. Sense of "matters pertaining to one's trade" is from 1814 (as in talk shop (v.), 1860).