Hi Yvonne,

There is a William Cosain of Patrick buried in 1850 at Brian Lawsons site. This is the nearest. There dont appear to be any instances of the name as you have it spelt at Frances Coakley's site.

One variant possibility could be Cosnahan, then it may also be Costean or Costain...... others may know of other possibililties too.

Good luck with your research.

Elizabeth