Is there a connection between this place and the Avalon myth?I suspect not; I'm no historian, but I think Avalon in the legend of King Arthur & his knights of the round table is believed (at least according to folklore) to be around in Glastonbury* in Somerset (south-west England).
That said, some believe it was even further west, near Tintagel in Cornwall; I hadn't heard of it being as far west as Ireland, though...
(*This is why the locals grumbled a bit when BF didn't sing Avalon when he played at the Glastonbury Abbey Extravaganza in 2013; all they got was the BFO's jazz instrumental version.)