While translating the dictionary to Swedish I came across the word Oblivion, translated "Oblivion". It seems obvious that this loan-word refers to the Daedric realms, and not the English word meaning 'forgetfulness, obscurity, nonexistence'. But I thought I'd better ask, just to be sure. Where is it attested?

~Zul

It refers to the Daedric realms, seen in the Word Wall for Nah in Whirlwind Sprint.

Nonvul bron dahmaan daar
rot do fin fodiiz bormah
Oblivion loost nid nah med
spaan vahdin beyn

Noble Nord, remember these
words of the Hoar Father - 
Oblivion hath no fury like
a shield maiden scorned.

Even ignoring the William Congreve reference, this Word Wall has some peculiar elements. "Oblivion" is used as a loanword (from a language that didn't exist at that point in Elder Scrolls history), and there is the sole usage of loost, which seems either a formal version of los or specifically a third person conjugation of los, which itself would be unusual because the dragon language doesn't conjugate verbs by person.

Very interesting indeed! Are we perhaps to infer that Oblivion is actually a genuine Dovahzuhl word which was eventually borrowed in Cyrodiilic via the Nords? Associating it with oblaan 'end' is tempting. Then again, the phonology of the word fits very poorly in the phonotax of the Dragon language.

Regarding loost 'hath' – the word is used in the sense 'possess', not as an auxiliary verb as in English "He has come". So it isn't necessarily a form of los 'is', is it? I see in the dictionary that there is also a verb lost 'have, was'; isn't it more likely that loost is a variant of this? An archaic variant, judging by the translation "hath".

Edit: on further consideration I realize that lost is probably regarded as an inflected form of los. Let's say los/lost covers the spectrum of 'is/was/has (been)/had (been)'. Maybe loost covers the sense of 'has' as purely a transitive verb "possess"?

You're right that oblivion does not fit the phonology of the dragon language. Whatever the explanation, there is something strange going on there.

Also, absolutely, lost is what I should have said instead of los.