The surname "Mertha" or "Mentha" or etc., is undoubtedly "Murtha" or originally "Murtagh" -- pronounced "mur-tah," accent on the first syllable. The surname "Murtha/Murtagh" is found in Co. Monaghan records which I have explored. The problem is in reading the tombstones, or old records, in which the records transcriber/tombstone chisler wrote "em as he heard 'em, especially if the transcriber was not Irish but English or in the US something else. I have this surname and sometimes (in Cincinnati, Ohio) it was rendered as "Mertha" or "Merta" because the Irish brogue interferred (and besides, the folks, themselves, often didn't know the "correct" spelling or was there one! The "Carrollan" surname quite possibly might have been rendered "Carolan." or other varietions thereof. Hope this helps. Sally M.