grub

From Middle English grubben, grobben, from Old English *grubbian, from Proto-West Germanic *grubb-, from Proto-Germanic *grubb- (compare Middle Dutch grobben (“to scrape, scramble, grab”), Old High German grubilōn (“to dig, search”), German grübeln (“to meditate, ponder”)), from Proto-Germanic *grub- (“to dig”) (see *grabaną).

The noun sense of "larva" is from Middle English grub, grubbe, grobbe, crubbe and may derive from the notion of "digging insect" from the verb above, or from the uncertainly related Middle English grub (“dwarfish fellow”). Compare West Frisian krobbe (“beetle”). The slang sense of "food" is first recorded 1659, and has been linked with birds eating grubs or with bub (“drink”).