English 'rider' and Old Norse 'riddari' look so similar that I suspect a common
Zoega's Old Icelandic dictionary (1926) has 'reið' (ride) and 'reiða' (to carry
on horseback). Inflected spellings of the latter include 'reiddr, reiddi'.
Just in case the Icelandic character doesn't come across, the last letter
in 'reið' is the letter that sounds like English 'th' in 'then'.
Zoega also lists "(1) rider, horseman (2) knight" in the entry for 'riddari'.
I don't know what methodology could confirm that the Irish word 'ridire' was
borrowed from Norse rather than English. Could linguistic methods do this? Or
is it a question purely for the historians? Liz