late 13c., "bright," from Old French cler "clear" (of sight and hearing), "light, bright, shining; sparse" (12c., Modern French clair), from Latin clarus "clear, loud," of sounds; figuratively "manifest, plain, evident," in transferred use, of sights, "bright, distinct;" also "illustrious, famous, glorious" (source of Italian chiaro, Spanish claro), from PIE *kle-ro-, from root *kele- (2) "to shout" (see claim (v.)).
The sense evolution involves an identification of the spreading of sound and the spreading of light (cf. English loud, used of colors; German hell "clear, bright, shining," of pitch, "distinct, ringing, high"). Of complexion, from ...
