/ˈkælɪbər/·noun·1560s in English, initially figurative: 'degree of merit or importance,' borrowed from Middle French calibre. The physical firearms sense — 'inside diameter of a gun barrel' — is attested from the 1580s.·Established
Origin
From Arabic qālib (a mold or template), caliber traveled through Ottoman artillery vocabulary into Spanish, Italian, French, and English, shifting from the bore-diameter of a cannon to a measure of human capacity.
Definition
The internal diameter of a gun barrel or cylindrical tube, and by extension the quality or level of someone's ability or character.
The Full Story
French (from disputed Arabic or Latin source)Mid-16th centurywell-attested
The etymology of 'caliber' is genuinely contested between two scholarlycamps. The traditional theory traces it as a borrowing from Arabic qālib ('a mold for casting, a last'), which is itself a borrowing — Arabic took qālib from Greek kalapous (καλάπους), meaning 'a shoemaker's last,' a compound of kalon ('wood') + pous ('foot'). Under this route, the word traveled from Greek craftwork vocabulary into Arabic during the era of Arab-Byzantine contact and the great translation
Did you know?
The same Arabic root that gave us caliber also gave us calipers — the measuring instrument. When Portuguese sailors introduced firearms to Japan in 1543, they brought the word along with the weapons: Japanese borrowed karibu from Portuguese calibre. A shoemaker's last in medieval Arabic became, five centurieslater, a measure of intellectual worth in English — the mold that once determined the size of a cannon ball now determines the size of a person's mind.
from Medieval Latin qua libra ('of what weight'), combining qua (ablative feminine of quis, from PIE *kwo-) with libra ('balance, scales'). Under this view, calibre began as a technical question — 'of what weight is this projectile?' — and was coined in French military contexts. English adopted calibre/caliber from French in the 1560s, initially in a figurative sense ('degree of merit'), then physically for gun barrels by the 1580s. Key roots: kalon + pous (Ancient Greek: "wood + foot — compound forming kalapous, a shoemaker's wooden last"), qālib (قالب) (Arabic: "a mold or form used for casting or shaping; borrowed from Greek kalapous"), *kwo- (Proto-Indo-European: "stem of interrogative and relative pronouns — source of Latin qua in the rival etymology qua libra").
calibre(French (borrowed from Arabic))calibro(Italian (borrowed from Arabic))calibre(Spanish (borrowed from Arabic))Kaliber(German (borrowed via French))qālib(Arabic (ultimate source))καλαπόδι (kalapódi)(Greek (from same Arabic root via Turkish))