*dnghū-, Proto-Indo-European root meaning "tongue."
It is the hypothetical source of/evidence for its existence is provided by: Latin lingua "tongue, speech, language" (from Old Latin dingua); Old Irish tenge, Welsh tafod, Lithuanian liežuvis, Old Church Slavonic jezyku "tongue;" Old English tunge "tongue; speech."
for historical evolution, see V. Used punningly for you by 1588 ["Love's Labour's Lost," V.i.60], not long after the pronunciation shift that made the vowel a homonym of the pronoun. As a simple shorthand (without intentional word-play), it is recorded from 1862. Common in business abbreviations since 1923 (such as U-Haul, attested from 1951).
The substitution of Middle English -o- for Old English -u- before -m-, -n-, or -r- was a French scribal habit before minims to avoid misreading the letters in the old style handwriting, which jammed them together. The practice transformed some, come, monk, tongue, worm.
by 1944, from Italian linguine, plural of linguina "little tongue," diminutive of lingua "tongue," from Latin lingua "tongue" (from PIE root *dnghu- "tongue").
"something in the shape of a little tongue," early 15c., from Old French languete (Modern French languette), literally "little tongue," diminutive of langue "tongue," from Latin lingua "tongue" (from PIE root *dnghu- "tongue"). As the name of a kind of hood in 17c. women's dress it probably is a separate borrowing of the French word.