late 17c., "a tool for digging," from dig (v.). Meaning "archaeological expedition" is from 1896. Meaning "a thrust or poke" (as with an elbow) is from 1819; figurative sense of this is by 1840.
c. 1200, diggen, "to make a ditch or other excavation," a word of uncertain origin, perhaps related to dike and ditch, either via Anglo-French diguer, from Old French digue "dike" (which is ultimately from Proto-Germanic *dīk-, from PIE root *dheigw- "to stick, fix") or directly from an unrecorded Old English verb. The older native words were deolfan (see delve), grafan (see grave (v.)).
Transitive meanings "form by excavation, make by digging," also "obtain or remove by excavation" are from late 14c.; figurative sense of "discover by effort or search" is from early 15c. Meaning "to penetrate" is from mid-15c.; transitive sense of "cause to penetrate, thrust or force in" is by 1885.
In 19c. U.S. student slang it meant "study hard, give much time to study" (1827); the 20c. slang sense of "understand" is recorded by 1934 in African-American vernacular. Both probably are based on the notion of "excavate." A slightly varied sense of "appreciate" emerged by 1939. The strong past participle dug appeared in 16c. but is not etymological.
1530s, "locality where mining is carried on," verbal noun from dig (v.). Diggings, colloquial for "lodgings, quarters" is by 1838.
mid-15c., "one who digs;" 1680s, "instrument for digging," agent noun from dig (v.). The communistic movement in England so called from 1649. Meaning "one who seeks gold in a prospecting place" is from 1853. In 19c. American-English, it was the name for degraded Native Americans in the West, who were so called for living chiefly upon dug-up roots (1837).
Proto-Indo-European root meaning "to stick, fix."
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dehi- "wall;" Old Persian dida "wall, stronghold, fortress," Persian diz; Latin figere "to fix, fasten, drive, thrust in; pierce through, transfix;" Lithuanian dygstu, dygti "germinate;" Old Irish dingid "presses, thrusts down;" Old English dic "trench, ditch," Dutch dijk "dam."
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.