Calnan is another family name that comes from county Cork, Ireland. Thre is Calnan containers currently inoperation. why don't you google the name & find some living Calnan family?
Branches of the McCarthy clan are usually diferentiated: main line McCarthy Mor descended from Saerbrethach (Justin)ad 925 & his son Carthach- then offshoots: McCarthy Reagh & McCarthy of Gleann-a-Chroim about 1203 descended from Donal Oge McCarthy . Also McCarthy of Dunmanway , Dunhallow, Sowney, Ardcanaughty, all diferentiated by adding a place name after McCarthy.
See the pedigree of McCarthy Mor, Reagh etc in 'Life & Letters of Florence McCarthy Reagh' by Daniel McCarthy Glas. Glas is abbreviation of Gleann-a-Chroim.
Also remember that the McCarthy families (plural) kept intermarrying so you need to know which house, hamlet, village as well as the town nearby & the county of Ireland your McCarthy family comes from originally.
Mine come from Garralacka near Clonakilty in County Cork, Ireland & some stil live on the orignal farm my gt grandfather Michael was born in.
You will just have to look & compare with my tree @Josephine Salt Familytree Halloween 2012'.