the.com/caliber

means The internal diameter of a gun barrel (or its bullet) — and by extension, a measure of someone's ability or worth.

from Traces through French 'calibre' back to Arabic 'qālib' (mold, shoemaker's last), the thing a form is shaped around — possibly influenced further back by Greek 'kalopous' (shoemaker's last, literally 'wood-foot'). It arrived in European languages as a term for gun-bore measurement before widening, by the 1800s, into a figurative gauge of a person's quality or stature.