clam up, Slang.to refuse to talk or reply; refrain from talking or divulging information: The teacher asked who had thrown the eraser, but the class clammed up.
Origin: 1585–95; short for clam-shell, i.e., bivalve with a shell that clamps. See clam2, shell
any of various burrowing bivalve molluscs of the genera Mya, Venus, etc. Many species, such as the quahog and soft-shell clam, are edible and Tridacna gigas is the largest known bivalve, nearly 1.5 metres long
2.
the edible flesh of such a mollusc
3.
informal a reticent person
—vb , clams, clamming, clammed
4.
chiefly (US) (intr) to gather clams
[C16: from earlier clamshell, that is, shell that clamps; related to Old English clamm fetter, Old High German klamma constriction; see clamp1]
c.1500, "bivalve mollusk," originally Scottish, from M.E. clam "pincers, vice, clamp," from O.E. clamm "bond, fetter," from P.Gmc. *klam-. Clambake is from 1835. Clam up is 1916, Amer.Eng., but clam was used in this sense as an interjection c.1350.
n. a dollar. (Underworld.) : You got a couple of clams I can bum for a little bottle?
n. a tight-lipped person. : Suddenly, she became a clam and wouldn't talk anymore.
Dictionary of American Slang and Colloquial Expressions by Richard A. Spears.Fourth Edition. Copyright 2007. Published by McGraw Hill.
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