Etymology
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big time (n.)

"upper reaches of a profession or pursuit," by 1909 in vaudeville slang. As an adjective by 1915. The same phrase was common in colloquial use late 19c.-early 20c. in a broad range of senses: "party, shindig, fun, frolic."

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piss off (v.)

1958, intransitive, "go away," chiefly British; the transitive meaning "annoy (someone)" is by 1968, chiefly U.S.; from piss (v.) + off (adv.). Pissed off "angry, fed up" is attested by 1946 (Partridge says 1937); said to have been used in the military in World War II; in common use from 1970s.

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time zone (n.)

by 1885, from time (n.) + zone (n.). As in Britain and France, the movement to regulate time nationally came from the railroads.

Previous to 1883 the methods of measuring time in the United States were so varied and so numerous as to be ludicrous. There were 50 different standards used in the United States, and on one road between New York and Boston, whose actual difference is 12 minutes, there were three distinct standards of time. Even small towns had two different standards one known as "town" or local time and the other "railroad" time.
... At noon on November 18, 1883, there was a general resetting of watches and clocks all over the United States and Canada, and the four great time zones, one hour apart, into which the country was divided came into being. So smoothly did the plan work that the general readjustment was accomplished without great difficulty and it has worked satisfactorily ever since. [Railroad Trainman, September 1909]
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get off (v.)

"escape," c. 1600, from get (v.) + off (adv.). Sexual sense attested by 1973.

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go off (v.)

1570s, of firearms, etc., "explode, be discharged;" see go (v.) + off (adv.); meaning "depart" is c. 1600; that of "deteriorate in condition" is from 1690s; that of "reprimand" is from 1941 (originally with at, since c. 2000 more often with on).

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back off (v.)

"retreat, stop annoying someone," by 1938, from the verbal phrase, from back (v.) + off (adv.).

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bug off (v.)

"leave quickly," by 1956, perhaps from bugger off (see bugger (v.)), which chiefly is British (by 1920s) but was picked up in U.S. Air Force slang in the Korean War. Also see bug (v.3). To bug out "leave quickly, scram" is from 1953.

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set off (v.)

verbal phrase; see set (v.) + off (adv.). From 1590s as "make prominent by contrast," 1610s as "adorn." Intransitive sense of "start on or as on a journey" is from 1774. Meaning "separate from contect" (in typography) is from 1824; sense of "ignite, discharge, cause to explode" is from 1810.

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beat off (v.)

"drive (something) away by violent blows," 1640s, from beat (v.) + off (adv.). The meaning "masturbate" is recorded by 1960s.

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