Green’s Dictionary of Slang

1. a non-Jewish woman.

1977

D. Powis Signs of Crime 184: Flour mixer (a) Yiddish rhyming slang for ‘shikse’ (girl domestic or shop assistant).

2. an insignificant person, esp. a clerk [ext. of sense 1; note orig. Yid. shikse means non-Jewish woman or a female servant].

1977

D. Powis Signs of Crime 184: Flour mixer [...] An inoffensive man, particularly a clerk.