> I think that "suabais serig" may be a cheville,
> too, meaning something like "silken soft, softness of silk".
> Both Ó Dónaill and Dwelly list "seiric" as meaning "silk", and
> this corresponds to "siric" in DIL, an indeclinable noun from
> Latin "sericum".
seiric has a voiceless /k/ at the end, as Mod. Ir. shows us. But we
need a voiced and lenited sound at the end for a rhyme with tenid. So
we don't get around seirig 'firm, resolute'.