numbles (n.)

word-forming element used since 19c. and meaning "loin, loins," from Latin lumbus "hip, loin" (usually plural), from Proto-Italic *londwo- "loins," from PIE *lendh- (1) "loin" (source also of Sanskrit randhra- "loin (of animals);" Old Church Slavonic ledvije (plural) "loins, kidneys, insides; soul," Russian ljadveja (archaic) "thigh;" Old English lendenu "loins," Old Norse lend, German Lende "loin," Lenden "loins").

to eat humble pie (1830) is from umble pie (1640s), pie made from umbles "edible inner parts of an animal" (especially deer), considered a low-class food. The similar sense of similar-sounding words (the "h" of humble (adj.) was not then pronounced) converged to make the pun. Umbles is Middle English numbles "offal," with loss of n- through assimilation into preceding article.