> Thanks for the detailed response, Llama Nom. I had thought the word
"einman" meant "alone", at least in Modern Icelandic, but maybe that
is indeed the only word for such in Old Norse - or maybe they had
another concept for that phenomenon back then. Well, just curious.

There's an indeclinable adjective 'einmana' "lonely, alone" which
existed in the medieval language and is still used. Old
Icelandic/Norse dictionaries also have an adjective 'einmani' with the
same meaning. Actually, on further investigation, it looks as if this
noun 'einman' may have been restricted to the phrase 'í einmani'
"alone" ('búa í einmani' "live in solitude"). The quotes in the
Cleasby/Vigfússon dictionary are from Norwegian law codes, so it's not
clear whether the word was also used in Iceland.

Two other possibilities that have been suggested to me: 'einsemd' and
'einvera'. These are both used nowadays; I'm not sure when the
earliest evidence for them dates from. They're not in
Cleasby/Vigfússon, but that doesn't necessarily mean that they weren't
used in early times. Another possibility I thought of is 'einseta',
but this is especially associated with solitide as a religious
discipline: a hermit's way of life, or the place where it is lived (a
hermitage).