Bar is a versatile word. Its definitions—as a noun—in the Oxford English Dictionary (Compact Edition) take up more than six columns. Some of the meanings are: a piece longer than it is wide, of wood, metal, stone, soap, chocolate, etc.; a heraldic device of two lines drawn horizontally across a shield; the transverse ridged divisions of a horse’s palate; that which confines, limits, or closes; a vertical line across a stave to divide a musical composition; a game also known as prisoner’s base; a legal plea of sufficient force to stop an action or order; an obstacle, a barrier; a court of law; the whole body of barristers (lawyers); a barrier separating the seats of spectators from the official portion of a court or other assembly, to which students were called when they had attained sufficient learning, hence the word barrister; a large European fish also known as a maigre; a barrier or counter over which food or drink is served, and hence, sometimes the whole establishment; a standard (as in raising the bar); a handrail used by ballet dancers for support while exercising (although balletomanes prefer the Frenchified spelling barre).
Its earliest meaning was apparently a “stake or iron rod used to fasten a door or gate.” The OED’s first instance was in 1175, when The Lambeth Homilies mention “the barren of helle.” Wyclif’s 1388 Bible uses the word in its rendition of Numbers Chapter 4 verse 10—“Thei schulen putte in barris,” which the King James Version has as They shall put it…upon a bar.”
By the 1580s bar meant a bank of sand in a harbor or river mouth (which is what Tennyson referred to in “Crossing the Bar”), and by 1833 soap came in bars. Not until 1906 did chocolate make it is appearance in that form. “Bar graphs” appeared 1925, “behind bars” meaning to be in prison in 1934 (although by 1642 Richard Lovelace told us that “stone walls do not a prison make/nor iron bars a cage”); and “bar code” in 1963.
As a verb, bar has several more columns in the OED.
The word first popped up in Middle English barre, adopted from Old French barre, a phonetic descendant of late Latin barra—which is, as you might have guessed, of unknown origin. Friedrich Diez, a 19th-century German etymologist, thought it came from Old Irish barr, meaning “bushy top”—but that theory has been dismissed by most linguists, who point out that it has no relationship to any of the meanings of the word.
The Bard of Buffalo Bayou knows of only kind of bar, out of which he has been tossed on numerous occasions for conduct unbecoming a poet.
“D. Boon kilt a bar”
Was carved upon a tree,
Not very circumspectly.
Just five words there are,
And if you look, you’ll see
Only one is spelled correctly.