Gaius, sometimes spelled Caius, was a common Roman praenomen. It is abbreviated C.; the abbreviation goes back to before the Roman alphabet distinguished between C and G, probably from Etruscan Cae or Cai, meaning unknown. In classical times, the name was pronounced in three syllables, Gā-ǐ-us .
It is also possible that the use of C reflects the Greek letter Gamma.
Some people with this name:
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