Etymology Inherited from Middle English basile, from Middle French basile, from Old French basile, from Medieval Latin basilicum, from Ancient Greek βασιλικόν (basilikón, “royal”), from βασιλεύς (basileús, “king”). Doublet of basilic, basilicon, and basilicum; further related to basileus, basilean, and basileiolatry.
These usually large chisels may have the edge basiled on either the inside or the outside of the 90° angle of the blade.1972, Alex W[inkler] Bealer, “Chiseling”, in Old Ways of Working Wood, Barre, Mass.: Barre Publishing Company, Inc., published March 1976 (2nd printing), →ISBN, page 148:
The angle to which a joiner's tool is ground away.
[H]old the edge of your Iron upvvards in your left hand and your VVhet-ſtone in your right, and having firſt ſpit upon your Stone to vvet it, apply it to the Baſil of your Iron, in ſuch a Poſition that it may bear upon the vvhole bredth of the Baſil; and ſo vvorking the Stone over the Baſil, you vvill quickly vvear the courſer grating of the Grind ſtone off the edge on that ſide: […]1678 April 11 – May 11 (Gregorian calendar), Joseph Moxon, “Numb[er] IV. The Art of Joynery.”, in Mechanick Exercises, or The Doctrine of Handy-Works, […], volume I, London: […] Joseph Moxon, published 1678, →OCLC, § 10 (Of Grinding and Whetting the Iron, and Other Edge-tools), pages 71–72:
basil
noun
Etymology Corrupted from English basan, from French basane, from Late Latin basanium, from Arabic بِطانَة (biṭāna, “lining”).
1
The skin of a sheep tanned with bark.
Each sleeper has for covering a large basil (dressed sheep-skin), such as cobblers use for aprons. As they lie in long rows, in the most profound repose, with these dark brown wrappers about them, they present the uniform look and arrangement of a long line of mummies.1851, Henry Mayhew, London Labour and the London Poor, published 1861:
Archaic, Historical A fetter fastened round the ankle of a prisoner.
When I once more feel that sharp smarting around the scabby sores that cluster like so many oysters on my ankles beneath my chained iron basils, I know that the tide has turned.2001, Richard Flanagan, Gould's Book of Fish, Vintage, published 2016, page 49: