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"British soldier," 1884, from Thomas Atkins, since 1815 the sample name for filling in army forms. Tommy gun (1929) is short for Thompson gun (see Thompson). Soon extended to other types of sub-machine gun, especially those favored by the mob.
late 14c., "a musical sound, a succession of musical notes," unexplained variant of tone. Meaning "state of being in proper pitch" is from mid-15c.
"bring into a state of proper pitch," c.1500, from tune (n.). Non-musical meaning "to adjust an organ or receiver" is recorded from 1887. Verbal phrase tune in in reference to radio (later also TV) is recorded from 1913; figurative sense of "become aware" is recorded from 1926. Tune out "to eliminate radio reception" is recorded from 1908; figurative sense of "disregard, stop heeding" is from 1928. Related: Tuned; tuning.
tomboy: The red-haired tommy ... she'd put him over the jumps (1940s+)
A private in the British army: He met three Tommys in a bar (1884+)