*Agronā was a hypothetical reconstructed Proto-Celtic name for the River Ayr in Scotland, later applied to the River Aeron in Wales. The claim is linguistic and first appeared in William J. Watson's Celtic Placenames of Scotland (1926).[1] Watson suggested the River Ayr in Scotland could be worked back to a hypothetical Proto-Celtic "river goddess of slaughter and carnage" and that the deity name was *Agronā.[2] At that time there were many questionable Scottish nationalist attempts to use the River Ayr place-name to claim Taliesin's battle poems for Scotland and Watson's derivation strongly and implicitly supported such claims.
It sounds a lot like a name from a fantasy story, and I'd probably use it for a female villain in a story. It strikes me as an excellent name for a female warlord. It sounds like it belongs to a stoat or a weasel or something (though probably this is because of Antrigra the stoat from the Redwall books).