My MGGM was Ellen Mountain of Rossorry. Her father was Robert Mountain of Rossorry, a tailor. She, then a spinster, married John Mountain of Rossorry, a tailor and a widower. His father was John Mountain, also a tailor. Marriage was 22 Dec 1857 at the Registrar's Office in Enniskillen. Looking for where in Rossorry and additional information.
As well as being the name of a Church of Ireland and Civil parish, Rossorry is also the name of a townland consisting of just over 164 acres. There doesn't ssem to be any Mountain properties listed in this townland on Griffith's Valuation which took place just a few years after the marriage in 1862. There's just one Mountain listing in Co. Fermanagh that I can see on Griffith's - a Thomas Mountain at Lisbane townland in Aghavea civil parish, which is to the southwest of Rossorry civil parish.(Rossorry parish is adjacent to Enniskillen)
Marriage certs give current residences for the bride and grrom, which may not be where they were from originally.