Etymology Dictionary

BAD,  evil, wicked.  (C.?)   M.E. bad, badde; Chaucer has badder, i.e. worse, C. T. 10538.   Not in use much earlier in English.   Rob. of Glouc. has badde, evil, p. 108, l. 17; and this is perhaps the earliest instance.   β. The word has hitherto remained unaccounted for; it is clear that the G. böse, Du. boos, bad, evil, is too unlike it to help us.   The Pers. bad, wicked, has a remarkable resemblance to the Eng. word, but can hardly have been known to Rob. of Glouc.   γ. I think we may rather account for it by supposing it to be Celtic.   The Cornish bad, foolish, stupid, insane, occurs in the miracle-play of the Resurrectio Domini, ll. 1776, 1886 (fifteenth century).   Mr. R. Williams says:  'this word is not extant in this sense in Welsh, but is preserved in the Armoric bad, stupidity.'   He might have added that it is plainly the Gael. baodh, vain, giddy, foolish, simple; baoth, foolish, stupid, profane, wicked, wild, careless; with numerous derivatives, such as baoth-bheus, immorality, misbehaviour.   This account seems sufficient.   δ. May we go so far as to connect the word further with the Lat. ped-us*, bad, supposed by Corssen to be the root of Lat. peior (ped-ior), worse, and pessimus (ped-timus), worst?   If so, the root is PAD, to fall [†]   ¶ The nearest Teutonic form is the Goth. bauths, deaf, dumb, insipid (said of salt); but I see no clear proof that E. bad is connected with it.   On the contrary, the Goth. bauths, deaf, is obviously the Gael. bothar, deaf; and Fick (i. 156) also cites Skt. badhira, deaf, from ✔BHADH, to bind.   Der. bad-ly, bad-ness.   The words worse, worst, are from a different root. 

ADDENDA

Section δ, which was merely a guess, should be cancelled.   It is hardly worth while to discuss further this difficult and much-disputed word.