1817, "rainy," from drip (n.) + -y (2). Meaning "sloppily sentimental" is 1944, from the slang sense.
Entries linking to drippy
drip n.
mid-15c., drippe, "a drop of liquid," from drip (v.). From 1660s as "a falling or letting fall in drops." Medical sense of "continuous slow introduction of fluid into the body" is by 1933. The slang meaning "stupid, feeble, or dull person" is by 1932, perhaps from earlier American English slang sense "nonsense" (by 1919).
-y 2
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.