| Calhoun | From the narrow forest. Surname. |
| Callaghan | An Irish name meaning brightheaded. |
| Callahan | An Irish name meaning brightheaded. |
| Callee | Variant of Cayley meaning from the forest |
| Callough | A slender and slim person. |
| Calvagh | Meaning the bald or hairless one. |
| Caly | A name meaning bud or flower pod. |
| Camlin | A name meaning a crooked or bent pool. |
| Camren | A variant of the name Cameron. |
| Camy | Variant of Camey: Champion. |
| Canice | Derived from the word for fire. |
| Caoimhe | Lovely and charming |
| Caoimhin | A gentle and handsome person. |
| Caolaidhe | One who is slender or graceful. |
| Caolan | A name meaning little slender one. |
| Caomh | Someone who is dear or beloved. |
| Capri | Named after the Italian island. |
| Caraid | A Gaelic word meaning true friend. |
| Carden | from the black fortress |
| Carleen | Feminine form of Charles manly |
| Carlin | Little champion |
| Carny | Variant of Carney: Champion; victorious. |
| Carraig | From the rocky headland |
| Carrick | From the rocky headland |
| Carroll | Feminine of Carl: joy |
| Carryl | love also see carol |
| Cartagh | Variant of Carthach: Loving. A variant of Caradoc. The Irish St. Carthach, also known as St Carthage, founded an early 7th century monastery at Lismore, County Waterford. |
| Carthach | A name meaning loving or affectionate. |
| Carthage | Derived from the new city of Tyre. |
| Case | Variant of Casey Alert: vigorous. |
| Casee | A variant spelling of the name Casey. |
| Casey | Brave: Vigilant. |
| Cashel | A stone fort or circular enclosure. |
| Casidhe | A clever or ingenious Irish person. |
| Cass | A short form of names like Cassandra or Cassidy. |
| Cassady | Variant of Cassidy: Intelligent; from Caiside; curly-headed. |
| Cassian | A Latin name meaning hollow or empty vessel. |
| Cassidy | Clever: Curly-headed. |
| Cat | A small domesticated mammal. |
| Catelyn | Variant of Katherine meaning pure |