Words with no etymological roots

In looking at The History of English one finds that some rather common words have an unknown etymology:

A good example is the word dog, etymologically unrelated to any other known word, which, in the late Middle Ages, suddenly and mysteriously displaced the Old English word hound (or hund) which had served for centuries. Some of the commonest words in the language arrived in a similarly inexplicable way (e.g. jaw, askance, tantrum, conundrum, bad, big, donkey, kick, slum, log, dodge, fuss, prod, hunch, freak, bludgeon, slang, puzzle, surf, pour, slouch, bash, etc).

Words like gadget, blimp, raunchy, scam, nifty, zit, clobber, gimmick, jazz and googol have all appeared in the last century or two with no apparent etymology, and are more recent examples of this kind of novel creation of words. Additionally, some words that have existed for centuries in regional dialects or as rarely used terms, suddenly enter into popular use for little or no apparent reason (e.g. scrounge and seep, both old but obscure English words, suddenly came into general use in the early 20th Century).

Sometimes, if infrequently, a "nonce word" (created "for the nonce", and not expected to be re-used or generalized) does become incorporated into the language. One example is James Joyce's invention quark, which was later adopted by the physicist Murray Gell-Mann to name a new class of sub-atomic particle, and another is blurb, which dates back to 1907.

English language enthusiasts will want to browse further down the page at the link to learn about words created by adoption, truncation, fusion, imitation, back-formation, and errors ("refudiate.")