The Collaborative International Dictionary of English v.0.48:

Clammy \Clam"my\, a. [Compar. Clammier; superl. Clammiest.]
   [Cf. AS. cl[=a]m clay. See Clam to clog, and cf. Clay.]
   Having the quality of being viscous or adhesive; soft and
   sticky; glutinous; damp and adhesive, as if covered with a
   cold perspiration.
   [1913 Webster]