calibre: [16] Calibre, and the related calliper, are of Arabic origin. They come ultimately from Arabic qālib ‘shoemaker’s last, mould’ (there is some dispute over the source of this: some etymologists simply derive it from the Arabic verb qalaba ‘turn, convert’, while others trace it back to Greek kalapoús, literally ‘wooden foot’, a compound formed from kalon ‘wood’, originally ‘firewood’, a derivative of kaiein ‘burn’, and poús ‘foot’).
English acquired the Arabic word via Italian calibro and French calibre. The original Western meaning, ‘diameter of a bullet, cannon-ball, etc’, derives from the Arabic sense ‘mould for casting metal’. Calliper [16], which originally meant ‘instrument for measuring diameters’, is generally taken to be an alteration of calibre. => calliper
