In reply to the query by Dennis Coffey: There is a Cellsech, one of the
seven daughters (read kinswomen) of Tarbin at Ath na Cell (on the river
Blackwater in Munster), if that helps you out. The reference is item
666.2 (pg. 111) P. O Riain, Corpus Genealogiarum Sanctorum Hiberniae.
The date for any of these individuals is anyone's guess.