Merriam-Webster's Collegiate® Dictionary, 11th Edition
CLAM
I. noun
Etymology: Middle English, from Old English clamm bond, fetter; akin to Old High German klamma constriction and perhaps to Latin glomus ball Date: before 12th century clamp , clasp ,
II. noun
Usage: often attributive
Etymology: 1clam; from the clamping action of the shells
Date: circa 1520
1. any of numerous edible marine bivalve mollusks living in sand or mud, a freshwater mussel, a stolid or closemouthed person, clamshell , dollar 3,
III. intransitive verb (clammed; clamming)
Date: 1636
to gather clams especially by digging, clammer noun