wishy-washy (adj.)

1610s, "over-diluted," from wash (n.) + -y (2). Sense of "feeble, weak" is from 1630s. Related: Washiness.

"to vacillate, hesitate, act in an irresolute manner," 1782, from the adverbial expression to stand shilly-shally (1703), earlier shill I, shall I (1700), a fanciful reduplication of shall I? (compare wishy-washy, dilly-dally, etc.). From 1734 as an adjective, by 1755 as a colloquial noun, "indecision, foolish trifling." Related: Shilly-shallying (1816); shilly-shallier; shilly-shallyer.