F.J. Byrne in 'Irish Kings and High Kings' names a dozen by the name of Fergus. They are well spread out but two were in Leinster.

There were also saints in Ireland by the name of Fergus. Many years ago I researched a site in a townland called Killybawn (White Church). I later discoved that in early times it was dedicated to Saint Fergus. That was in county down, but the point I am trying to make is:

There were many Kings and Saints called Fergus. Therefore, it is reasonable to conclude that Fergus must have figured prominently in early placenames which have been lost and forgotten in the mists of time.

Sean