Etymology
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T and A (n.)
1972, short for tits and ass (a phrase attributed to Lenny Bruce), in reference to salacious U.S. mass media; earlier it was medical shorthand for "tonsils and adenoids" (1942).
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T 

twentieth letter of the English alphabet; in the Phoenician alphabet the corresponding sign was the 22nd and last; everything after T in the modern alphabet represents European alterations or additions. The sound has been consistent throughout its history.

In Late Latin and Old French, -t- before -e- and -i- acquired the "s" value of -c- and words appeared in both spellings (nationem/nacionem) and often passed into Middle English with a -c- (nacioun). In most of these the spelling was restored to a -t- by or in the period of early Modern English, but sorting them out took time (Edmund Coote's "English Schoole-maister" (1596) noted malicious/malitious) and a few (space, place, coercion, suspicion) resisted the restoration. 

To cross one's t's(and dot one's i's) "to be exact" is attested from 1849. Phrase to a T "exactly, with utmost exactness" is recorded from 1690s, though the exact signification remains uncertain despite much speculation. The measuring tool called a T-square (sometimes suggested as the source of this) is recorded by that name only from 1785. The T-cell (1970) so called because they are derived from the thymus. As a medieval numeral, T represented 160. A T was formerly branded on the hand of a convicted thief.

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T-bone (n.)
type of steak, 1916, so called from the T-shaped bone that runs through it. The verb meaning "to strike (another car, bus, etc.) from the side" is by 1970, from adjectival use in reference to crashes, attested from 1952, from the position of the two vehicles at impact.
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T-shirt (n.)
1920, in reference to the shape it makes when laid out flat (t-shirt is thus incorrect).
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abs- 
the usual form of ab- before -c-, -q-, or -t-.
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os- 
frequent form of ob- before -c- and -t- in words from Latin.
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amongst (prep., adv.)

"among," mid-13c., amonges, from among with adverbial genitive -s. The unetymological -t first attested 16c. (see amidst).

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stent (n.)
"tube implanted temporarily," 1964, named for Charles T. Stent (1807-1885), English dentist.
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toc 
word used for the letter -t- in radio communication, 1898. Compare ack (-a-), emma (-m-).
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whilst (adv.)
late 14c., from while (q.v.) with adverbial genitive -s-, and unetymological -t (see amidst).
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