"food," originally especially "Chinese food," 1856, American English (originally in California), from Chinese pidgin English chow-chow (1795) "food; mixed pickle or preserve; mix or medley of any sort," perhaps a reduplication of Chinese cha or tsa "mixed," or Cantonese chaau "to fry, cook." Hence also chow-chow (adj.) "mixed" (1845), since used as a noun in reference to various preserves or relish.
The dog breed of the same name is from 1886, of unknown origin, but some suggest a link to the Chinese tendency to see dogs as edible.