I'm not an expert on Welsh although I was aware that 'ci' is 'dog'. However, I would have expected the 'c' to become a 'g' in this position (in the same way as in Llanfair the 'M' of Mair has become an 'F')
Other examples are: carreg to mynyddygarreg; pont [bridge] to penybont; mynydd [mountain] to Llanbadarnfynydd, and of course Cymru [Wales] to Croeso i Gymru [Welcome to Wales].
So perhaps the corruption is more likely. But I'm sure a Welsh person will correct me if I am, ahem, barking up the wrong tree!