Tilting or turning something (like your head) at an angle, or preparing a weapon by pulling back its firing mechanism.
From 'cock' (Old English cocc, a rooster, also a valve or tap). The gun meaning comes from cocking a rooster's tail up—the mechanism resembles a rooster's posture.
Dogs cock their heads when confused because they're trying to hear better with one ear while using their eyes differently—it's a clever biological hack that humans adopted as a sign of curiosity.
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