Where does the word "dog" come from?

I discovered on a quiz show the other day that the word "dog" appears to have come from nowhere and displaced the German word "hund".

Has any research revealed how it arrived in the English language?

Solution 1:

The Wiktionary entry for "docga" suggests a possible origin in the root of a word originally meaning "power, strength, muscle" along with a diminutive suffix -ga.

It occurs to me that single-syllable words (or single syllables plus a suffix) can come about onomatopeoiacally. The root "dog"/"doc" doesn't necessarily have had to have come from "somewhere".

If the Wiktionary entry is correct that there is only one known attestation of "docga", it is striking that it became the word that eventually ousted "Hund" (as the generic word). On the other hand, I guess it's possible that "docga" was widely used, just not in the kinds of register that tended to be written down. (It's quite common for words to shift register over the years.)

Solution 2:

I believe the etymology of dog is still unknown. The following is from Etymonline.com:

O.E. docga, a late, rare word used of a powerful breed of canine. It forced out O.E. hund (the general Germanic and IE word; see canine) by 16c. and subsequently was picked up in many continental languages (cf. Fr. dogue (16c.), Dan. dogge), but the origin remains one of the great mysteries of English etymology.