| Claybourn | Dweller near the clay brook. |
| Clayd | A variant spelling of Clyde. |
| Claytan | A variant spelling of Clayton. |
| Cleland | From a place with clay |
| Clemencio | Meaning merciful and gentle. |
| Clementino | A gentle and kind individual. |
| Clenton | From the town on the hillside. |
| Cliffeton | From the town by the cliff. |
| Clifftan | Dweller near the steep cliff. |
| Clifften | One from the cliff settlement. |
| Cliffy | A diminutive of cliff dweller. |
| Cliften | From the farm by the cliff. |
| Clindon | From the hill near the cliff. |
| Clintan | Dweller of the stony settlement. |
| Clinten | One from the rocky enclosure. |
| Clintin | From the settlement on a hill. |
| Cloud | Named after the fluffy sky vapor. |
| Clyndon | From the hill of the famous. |
| Clyne | Dweller near the river bank. |
| Clyntan | Derived from a settlement near a hill. |
| Clynten | Variant meaning town by the hill. |
| Clynton | Old English for town on a hill. |
| Clyntwood | A forest located near a cliff. |
| Clywd | Named after a river in North Wales. |
| Co | Short form meaning company or unity. |
| Coal | Refers to the black mineral fuel. |
| Coale | An archaic spelling for charcoal. |
| Cobe | A variant of the name Jacob or Jake. |
| Cobey | A variant of the name Colby. |
| Coenbehrt | A variant of Coenbert. |
| Coenradd | A bold and wise counselor. |
| Coirbre | A charioteer or bold hero. |
| Colie | A diminutive form of Nicole. |
| Colmann | A variant of the name Colman. |
| Colte | A name meaning young horse. |
| Commodore | A title meaning a naval commander. |
| Coner | An Irish name meaning a lover of hounds. |
| Connaire | An Irish name meaning a hound of the sea. |
| Conri | An Irish name meaning a wolf king. |
| Consalvo | A name meaning a battle or war savior. |