It could be the -ide in "atthiraride", in some kind of case. - Edit 1
Before modification by Legolas at 14/04/2010 11:49:16 PM
Which would fit with your -at = infinitive conclusion, which I think is likely correct, and then we'd have a noun "thira" with article "at", or possibly just a noun "atthira".
(I had been thinking about the same thing before, that's why I can answer so fast now.
)
(I had been thinking about the same thing before, that's why I can answer so fast now.
)