1690s, "feeble or poor in quality," reduplication of washy "thin, watery" (see wash (n.)). Meaning "vacillating" first recorded 1873.
Marked by imprecision and vacillation; inconstant; uncertain: The wishy-washy player keeps putting off the evil day/ It's not overpowering like Opium and not wishy-washy
[1873+; fr a rhythmic reduplication of washy, ''weak, diluted, watered-down,'' probably influenced by wishy as suggesting vacillating desires; the original sense was ''weak, insubstantial, trashy,'' found by 1703]