suety Isaac, n. — Green’s Dictionary of Slang

suety Isaac n.

also soapy Isaac

[? its sallow ‘complexion’, supposedly reminiscent of a Jew; i.e. the ‘Jewish’ proper name Isaac]

a suet pudding.

1937–84

Partridge DSUE (1984) 1109/1: soapy Isaac See suet(t)y Isaac. [Ibid.] 1175/1: suet(t) Isaac. Suet pudding [...] 1904: ob. by 1930.