"digger," late 13c. as a surname; 1590s as a tool, agent noun from grub (v.). Meaning "one who gets wealth contemptibly" is from 1570s.
Entries linking to grubber
grub v.
c. 1300, "dig in the ground," from hypothetical Old English *grybban, *grubbian, from West Germanic *grubbjan (source also of Middle Dutch grobben, Old High German grubilon "to dig, search," German grübeln "to meditate, ponder"), from PIE *ghrebh- (2) "to dig, bury, scratch" (see grave (n.)). Transitive sense "dig up by the roots" is from 1550s. Related: Grubbed; grubbing.