Definition of dam up:
"o'erspread with a damp sweat and holy fear -
Dryden"
(n) :
moisture; humidity; fog; fogginess; vapor; dejection; depression; cloud of the mind
"night . . . with black air Accompanied, with damps and dreadful gloom. -
Milton"
(v) :
to
dampen; to render damp; to moisten; to make humid, or moderately wet; as, to damp cloth; to put out, as fire; to depress or deject; to deaden; to cloud; to check or restrain, as action or vigor; to make dull; to weaken; to discourage