1898 as a type of chair, from ladder (n.) + back (n.).

"words pronounced or written backwards or nearly so," 1860, from back (adj. or adv.) + slang (n.).

also, especially as an adjective, backdoor, "door at the rear of a building or other structure," 1520s, from back (adj.) + door (n.).

As an adjective, "devious, shady, illegal," by 1640s. The notion is of business done out of public view. The association with sodomy is from at least 19c.; compare also back-door man "a married woman's lover," African-American vernacular, early 20c.

in figurative sense of "withdraw a charge," 1859, American English, from the notion of descending a ladder, etc. (such a literal sense is attested by 1849); from back (v.) + down (adv.).

"physically demanding" (of manual labor), 1849; see back (n.) + break (v.).

"a strong beat regularly falling on a normally unaccented beat of a bar," 1928, in jazz, from back (adj.) + beat (n.). Later also in popular music.

also pullback, 1660s, "act or action of pulling back," from the verbal phrase; see pull (v.) + back (adv.). From 1951 in the military sense of "orderly withdrawal of troops."

also markup, "amount added by a retailer to cover overhead and provide profit," 1899, from the verbal phrase in this sense (by 1870); see mark (v.) + up (adv.).

"advance toward maturity," 1530s, from grow (v.) + up (adv.). As a command to be sensible, from 1951.

c. 1300, "suspend (something) so that it is supported only from above;" see hang (v.) + up (adv.); telephone sense by 1911. The noun hang-up "psychological fixation" is first attested 1959, from notion of being suspended in one place.