Snæbjörn reit:

> I had found an Icelandic dictionary but wasn't sure if
> the words in it would have been correct for the time
> period. The name would have been Fljottroxi.

No, it wouldn't. You're making all the same assumptions
as before. You cannot take two words out of an Icelandic
dictionary, string them together and expect the result
to be a valid word.

In this case you've probably found the Icelandic words
'fljótur' and 'öxi'. One way to make a compound out of
the two would be to put the noun in the genitive case
and tack it on to the adjective to make a new adjective:
'axarfljótur'. Another would be to tack the root-form
of the adjective on to the noun to make a new noun:
'fljótöxi'. Those are two grammatically valid words
(though they sound, to me, a bit silly).

So how do you know this when you just have your dictionary?
The answer is that you don't. You have to know the grammar
of a language in order to make new compounds in it.

Another issue is that when you don't know a language at all
it is easy to make mistakes. In this case 'fljót(u)r' has
somehow got corrupted to 'fljottr'.

Kveðja,
Haukur