In a nutshell:
PIE inflectional *-s became voiced in PGmc., giving *-z (= early
Runic <-R>). Its further development in Scandinavian was -r.
Rhotacism, or the lenition *z > r, is a fairly common process, cf.
Latin intervocalic *-s- > *-z- > -r- (tempus : temporis, flo:s :
flo:ris).
PIE *gHostis > PGmc. *gastiz (Runic gastiR) > ON gestr 'guest'
PIE *gHostejes > PGmc. *gastijiz > *gasti:z > ON gestir 'guests'
PGmc. *gaizaz > ON geirr 'spear'
(Note the shortening or loss of unstressed vowels.)
The further fates of the final -z (-R) were pretty complicated and
differed from one Old Norse dialect to another. It was often
assimilated to the preceding consonant after the intervening
unstressed vowel had been lost:
*stainaz > *stainR > steinn 'stone'
*sto:laz > *sto:lR > stóll 'chair'
*i:saz > *i:sR > íss 'ice'
There were some characteristic dialectal developments:
Proto-Norse *mannR > OIc. maðr (acc. mann) 'man'
In Old Swedish an epenthetic reduced vowel (written <e>) appeared
before a stem-final consonant and unassimilated -r. A similar
epenthesis has taken place in Modern Icelandic and Faroese (where the
spelling is <u>):
*xringaz > OSw. ringer; OIc. hringr > ModIc. hringur 'ring'
*fiskaz > OSw. fisker; OIc. fiskr > ModIc. fiskur 'fish'
In the later history of the Scandinavian languages (except Icelandic
and Faroese) the declensional system was radically simplified. In
particular, the nom. and acc.sg. of masculine nouns were levelled out
and the nom.sg. -r ending (OSw. -er) was dropped. This was a
morphological, not a phonetic proces, so -(e)r of other origin was
unaffected.
Piotr
--- In cybalist@..., malmqvist52@... wrote:
> Hi Miguel Carrasquer Vidal <mcv@...> wrote:
> > On Mon, 19 Nov 2001 22:50:09 -0000, malmqvist52@... wrote:
> >
> > >So maybe it's time for me to learn Old Norse, and if someone
here
> > >knows what the r stands for please tell me!
> >
> > IE *-s (nom.masc.sg. *-s, nom.pl. *-es, etc.)
> >
>
> I'm sorry, but I don't understand this either. Would it be possible
> to get a more detailed explanation?
>
> Best wishes
> Anders