Hi Melanie. I did find some information on the origin of the surname MacSherry. It's online at the following site.http://homepage.tinet.ie/~donnaweb/info/index.html#Personal
Once on the site, use the "search on this page" feature of your browser and it will take you directly to the part of the page that mentions the MacSherry. The site's name is Coats of Arms of Ireland and Around the World. Hope this helps.