Green’s Dictionary of Slang

grub n.1

[SE grub, the larva of an insect]

1. [mid-17C–18C; 1940s+] ‘a person of slovenly attire and unpleasant manners’ (OED).

2. [mid-18C+] a dirty, unkempt person, esp. a child.

3. [1950s] (Aus.) tuberculosis.

4. [1960s] (US teen) one who fails to achieve the popular social norms.

5. [1960s] (US campus) a student kitchen worker.