Caliber is the measurement of the inside width of a gun barrel or the diameter of a bullet. It can also mean the quality or ability level of a person or thing.
From French 'calibre,' probably from Arabic 'qālib' meaning 'mold' or 'model,' used for casting metal. The word moved into European languages with firearms technology. The leap from physical size to 'quality level' came later as a metaphor.
When we say someone is 'of a high caliber,' we’re borrowing gun vocabulary to talk about human quality. The original idea was about fitting a bullet to a barrel; now it’s about fitting a person to a task. It’s a reminder of how much military technology quietly shapes everyday language.
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