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" (source also of Old High German scopf "building without walls, porch," German dialectal Scopf "porch, cart-shed, barn," German Schuppen "a shed"), from a 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.
The meaning "building or room set aside for sale of merchandise" is from mid-14c. The meaning "schoolroom equipped for teaching vocational arts" is from 1914, American English (as in shop class, attested by 1948).
The sense of "one's own business, craft, or calling" is from 1814, as in talk shop (v.), "converse in general society about matters pertaining to one's trade," which is attested by 1860. Shop-talk (n.) is by 1881.
also barbershop, 1570s, from barber + shop (n.). Earlier in same sense was barbery (c. 1500). Barber-shop in reference to close harmony male vocal quartets is attested from 1910; the custom of barbers keeping a musical instrument in their shops so waiting customers could entertain themselves is an old one, but the musical product formerly had a low reputation and barber's music (c. 1660) was "wretched, poorly performed music."
"boy employed in a shop," 1813, from shop (n.) + boy (n.). Shopman as "assistant in a shop" is by 1758. Shop-girl , also shopgirl, "girl employed in a shop" is by 1820; earlier it meant "a domestic servant who assists in shopping" (by 1781); shop-maid is from 1650s; shop-woman from 1753. Genderless shop-assistant is by 1812, British English; slang shoppie (or shoppy) is by 1909.