I was looking at this word in some book or other a while ago — my ageing memory fails to remind me which — and wondered how such a collection of letters could have come together to make an adjective that meant bad-tempered, argumentative or uncooperative.
On looking into its antecedents, I found that cantankerous isn’t especially old by historical timescales. It appeared here first in something that resembled its modern form:
That’s because you don’t know her as well as I. Ecod! I know every inch about her; and there’s not a more bitter cantanckerous toad in all Christendom.
She Stoops to Conquer, by Oliver Goldsmith, 1773.
A curiosity of this passage is that it appears in numerous places as “bitter cantankerous road”, an unfortunate error that led the late Ivor Brown to base a molehill of discursiveness on this pimple of misinformation by reasoning falsely that it could apply to things as well as people. The fault is traceable to a misprint in volume two of Farmer and Henley’s Slang and its Analogues of 1891, which quotes only the last part of the excerpt, so denuding it of the context that would expose the error. (We may forgive the absence of the second c from cantanckerous, which modern editions of the play also omit.) The error has been perpetuated by writers who borrow the quote without troubling themselves to check the original.
It must indeed have been new in Goldsmith’s day, for the good Doctor Johnson didn’t give it house room in his Dictionary of 1755. It may be that he felt it was too slangy for him — Farmer and Henley called it “colloquial” more than two centuries later. But for Goldsmith it already had the sense we know today, of a person with a quarrelsome, cross-grained, ill-natured personality.
One proposal is that it was a blend of two words, each of which by itself suggested its sense: contentious and rancorous. But it’s also argued that it can be traced to the Middle English conteke, contention or quarrelling, via its compound conteckour, a person who causes strife. The latter word may have later changed spelling under the influence of these other words.
Either way, its sound is appropriate to its sense, evoking jangling metal objects, and that may be why it has survived and prospered, even without that extra letter.