The Fennas word for cat is cath. Cath is a last name. Cath means battle in Irish and Scots Gaelic.
How did I come up with this word? The Welsh word for cat is cath, the Irish word for cat is cat(!), and the Breton word for cat is kazh.
Not much to play with here. I haven't been using the letters K or Z, as in the Breton word. Both the Welsh and the Breton words end in H, so I thought I would do that in Fennas. My word for cat ends up being the same as Welsh (and Cornish).