The Monochan’s possibly came from the Mohill district in Leitrim, Ireland, near where there the McPartlin’s lived. Monochan is a common name in the area – dating back to at least 500 AD when Saint Monachan founded a monastery there.   

Monochan Name History
The name Monahan or Monaghan is chiefly to be found in the counties of Galway, Mayo and Fermanagh, all of which are not far from the original habitat of the O’Monaghans – that part of the Co. Roscommon which les between Elphin and Jamestown. The Manachan from whom the family takes its name was a famous Connacht warrior of the ninth century.