delve

Etymology 1

From Middle English delven, from Old English delfan (“to dig, dig out, burrow, bury”), from Proto-Germanic *delbaną (“to dig”), from Proto-Indo-European *dʰelbʰ- (“to dig”). Cognate with West Frisian dolle (“to dig, delve”), Dutch delven (“to dig, delve”), Low German dölven (“to dig, delve”), dialectal German delben, telben (“to dig, delve”).

verb

1. (intransitive) To dig into the ground, especially with a shovel.
2. (transitive, intransitive) To search thoroughly and carefully for information, research, dig into, penetrate, fathom, trace out
   She was intensely eager to delve into the mystery of Mr. Joplin and his brief case. 1943, Emile C. Tepperman, Calling Justice, Inc.!
3. (transitive, intransitive) To dig; to excavate.
   And then they made an oratory behind the altar, and would have dolven for to have laid the body in that oratory […] 1483, Jacobus de Voragine, translated by William Caxton, The Golden Legend
   They dolve a grave beneath the arrow And covered it with brere. 1865, Sebastian Evans, Brother Fabian's Manuscript: And Other Poems, page 59
   Let him take off his plates and delve himself, if delving must be done. 1891, Arthur Conan Doyle, chapter IV, in The White Company

Etymology 2

From Middle English delve, delf, dælf, from Old English delf, ġedelf (“digging”) and dælf (“that which is dug out, delf, ditch”). More at delf.

noun

1. (now rare) A pit or den.
   I put the clods on top the delve and gave it all a good thumping down with my feet. 1995, Alan Warner, Morvern Callar, Vintage, published 2015, page 75