1610s, "over-diluted," from wash (n.) + -y (2). Sense of "feeble, weak" is from 1630s. Related: Washiness.
Entries linking to washy
wash n.
late Old English wæsc "act of washing," from wash (v.). Meaning "clothes set aside to be washed" is attested from 1789; meaning "thin coat of paint" is recorded from 1690s; sense of "land alternately covered and exposed by the sea" is recorded from mid-15c.
-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.
wishy-washy adj.
1690s, "feeble or poor in quality," reduplication of washy "thin, watery." Meaning "vacillating" is attested by 1873.