Word Origin & History
O.E. sceaft "long, slender rod of a staff or spear," from P.Gmc. *skaftaz (cf. O.N. skapt, O.S. skaft, O.H.G. scaft, Ger. schaft, Du. schacht, not found in Gothic), which some connect with a Gmc. passive pp. of PIE base *(s)kep- "to cut, to scrape" (cf. O.E. scafan "to shave") on notion of "tree branch
stripped of its bark." But cf. L. scapus "shaft, stem, shank," which appears to be a cognate. Meaning "beam or ray" (of light, etc.) is attested from c.1300. Vulgar slang meaning "penis" first recorded 1719. Verb meaning "treat cruelly and unfairly" is 1950s, with overtones of sodomy.
"long, narrow passage sunk into the earth," 1433, probably from shaft
(1) on notion of "long and cylindrical," perhaps as a translation of cognate Low Ger. schacht in this sense (Grimm's suggestion, though OED is against it). Or it may represent a separate (unrecorded) development
in O.E. directly from P.Gmc. *skaftaz in the original sense of "scrape, dig." The double sense of shaft is attested in country music song title, "She Got the Gold Mine, I Got the Shaft."