Green’s Dictionary of Slang

nincum noodle n.

[nincompoop n. + noodle n.1 (2); punning on a SE noodle with no income]

a penniless fool.

[UK]‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 126: Nincum Noodle see Noodle. Nincum is a contraction of no income, i.e. not enough, or poverty.