The change of Latin f- to Spanish h- is characteristic; compare hablar from fabulari, hacer from facere, hecho from factum, hermoso from formosum. Confusion of initial h- and f- was common in 16c. Spanish; the conquistador is known in contemporary records as both Hernando and Fernando Cortés.
"person hired to do routine work," c. 1700, ultimately short for hackney "an ordinary horse, horse for general service (especially for driving or riding, as opposed to war, hunting, or hauling)," c. 1300. This word is probably from the place name Hackney, Middlesex. Apparently nags were raised on the pastureland there in early medieval times. Extended sense of "horse for hire" (late 14c.) led naturally to "broken-down nag," and also "prostitute" (1570s) and "a drudge" (1540s), especially a literary one, one who writes according to direction or demand. Sense of "carriage for hire" (1704) led to modern slang for "taxicab." As an adjective, 1734, from the noun. Hack writer is first recorded 1826, though hackney writer is at least 50 years earlier. Hack-work is recorded from 1851.
HACK. A hackney coach. The term hack is also frequently applied by women to any article of dress, as a bonnet, shawl, &c., which is kept for every day use. [Bartlett, "Dictionary of Americanisms," 1848]
Perhaps influenced by Old Norse höggva "to hew, cut, strike, smite" (which is unrelated, from PIE *kau- "to hew, strike;" see hew). Slang sense of "cope with" (as in can't hack it) is first recorded in American English 1955, with a sense of "get through by some effort," as a jungle (phrase hack after "keep working away at" is attested from late 14c.). To hack around "waste time" is U.S. slang, by 1955, perhaps originally of golfers or cabbies. Related: Hacked; hacking.