Covered with, containing, or resembling gravel; also can describe a rough, harsh voice or sound.
From gravel + -y (adjective suffix). The voice meaning likely developed metaphorically from the rough, gritty texture of actual gravel.
That gravelly voice you hear in old blues singers or smokers? It's literally describing vocal cords that have become rough and abraded, producing a texture similar to gravel—a perfect example of how body changes create linguistic descriptions.
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