Bullshit (also bullcrap, bullplop, bullbutter, horseshit) is a common American English expletive which may be shortened to the euphemism bull or the initialism B.S. In British English, "bollocks" is a comparable expletive, although bullshit is now commonly used in British English as well.

"Bull", meaning nonsense, dates from the 17th century, while the term "bullshit" has been used as early as 1915 in American slang, and came into popular usage only during World War II. The word "bull" itself may have derived from the Old French boul meaning "fraud, deceit" (Oxford English Dictionary). The term "horseshit" is a near synonym.

The earliest attestation mentioned by the Concise Oxford English Dictionary is in fact T. S. Eliot, who between 1910 and 1916 wrote an early poem to which he gave the title "The Triumph of Bullshit", written in the form of a ballade. The first stanza goes:

Ladies, on whom my attentions have waited
If you consider my merits are small
Etiolated, alembicated,
Orotund, tasteless, fantastical,
Monotonous, crotchety, constipated,
Impotent galamatias
Affected, possibly imitated,
For Christ's sake stick it up your ass.

The word bullshit does not appear in the text of the poem, though in keeping with the ballade form, the refrain "For Christ's sake stick it up your ass" appears in each following verse and concludes the envoi. Eliot did not publish this poem during his lifetime.

As to earlier etymology the OED cites bull with the meaning "trivial, insincere, untruthful talk or writing, nonsense". It describes this usage as being of unknown origin, but notes the following: "OF boul, boule, bole fraud, deceit, trickery; mod. Icel bull ‘nonsense’; also ME bull BUL ‘falsehood’, and BULL verb, to befool, mock, cheat." Worthy of note is the South African English equivalent "bull dust".

Although as the above makes clear there is no confirmed etymological connection it might be noted that these older meanings are synonymous with the modern expression "bull" otherwise generally considered, and intentionally used as, a contraction of "bullshit".