blow-job n.

"move air, produce a current of air," Middle English blouen, from Old English blawan "to blow (of the wind, bellows, etc.), breathe, make an air current; kindle; inflate; sound" a wind instrument (class VII strong verb; past tense bleow, past participle blawen), from Proto-Germanic *blæ-anan (source of Old High German blaen, German blähen), from PIE root *bhle- "to blow."

The transitive sense of "carry by a wind or current of air" is from c. 1300; that of "fill with air, inflate" is from late 14c. Of noses, from 1530s; of electrical fuses, from 1902. The meaning "to squander" (money) is from 1874; that of "lose or bungle" (an opportunity, etc.) is by 1943. The sense of "depart (some place) suddenly" is from 1902.

As a colloquial imprecation by 1781, associated with sailors (as in Popeye's "well, blow me down!"); it has past participle blowed.

To blow (a candle, etc.) out "extinguish by a current of air" is from late 14c. To blow over "pass" is from 1610s, originally of storms. To blow hot and cold "vacillate" is from 1570s. To blow off steam (1837) is a figurative use from steam engines releasing pressure. Slang blow (someone or something) off "dismiss, ignore" is by 1986. To blow (someone's) mind was in use by 1967; there is a song title "Blow Your Mind" released in a 1965 Mirawood recording by a group called The Gas Company.

 For the sexual sense, see blow-job. 

"piece of work; something to be done," 1620s, from phrase jobbe of worke (1550s) "task, piece of work" (contrasted with continuous labor), a word of uncertain origin. Perhaps a variant of gobbe "mass, lump" (c. 1400; see gob) via sense of "a cart-load." Specific sense of "work done for pay" first recorded 1650s.

job. (1) A low mean lucrative busy affair. (2) Petty, piddling work; a piece of chance work. [Johnson's Dictionary]

Meaning "paid position of employment" is from 1858. Printers' slang sense "piece of work of a miscellaneous class" (posters, handbills, etc.) is from 1795, hence job-type (notably large or ornamental or of exceptional form), job-shop, etc. Job lot (1832) is from an obsolete sense of "cartload, lump," which might be a separate formation from gob.

The very broad general sense of "occurrence, business, state of things" is colloquial from c. 1700. In modern slang or colloquial use, "an example," especially a good one (of the thing indicated), 1927, "a term of wide application" [OED]. Thieves' slang sense of "theft, robbery, a planned crime" is from 1722. Slang meaning "specimen, thing, person" is from 1927. On the job "hard at work" is from 1882. Job security attested by 1932 (job insecurity by 1936); job description by 1920; job-sharing by 1972. Job-hunter is from 1928. The phrase job of work still appears as late as Trollope (1873).