Merriam-Webster's Collegiate® Dictionary, 11th Edition
PEBBLE
I. noun
Etymology: Middle English pobble, from Old English papolstān, from papol- (of unknown origin) + stān stone
Date: 14th century
a small usually rounded stone especially when worn by the action of water, transparent and colorless quartz ; rock crystal , an irregular, crinkled, or grainy surface, pebbly adjective
II. transitive verb (pebbled; pebbling)
Date: 1605
to pelt with pebbles, to pave or cover with pebbles or something resembling pebbles, to grain (as leather) so as to produce a rough and irregularly indented surface