Given your username, I'd assume it's named after the character that Ken Curtis played on 'Gunsmoke'. I'll assume you know that Ken Curtis was also John Ford's son-in-law, and was in a number of John Wayne's movies, most notably 'Rio Grande' and 'The Searchers'. In 'Rio Grande' he was the lead singer for the 'Sons of the Pioneers', taking the lead in 'I'll Take You Home Again Kathleen'. In 'The Searchers' he played the guitar playing mail carrier and sometimes law-man Charlie McCorry, who was slated to wed Laurie Jorgensen (Vera Miles) until Martin Pawley, played by Jeffrey Hunter, returned home.
By all accounts, Ken Curtis was a fine man; friendly, gentle, and good to know. These traits could also be said about the real John Wayne.
Actually Festus was himself named after someone and thats where I got mine. When my first kid was on the way and the family asked what I’d name it I said, “Either Festus or Crispus” depending.
Both are New Testament names.
Naturally I didn’t name my kids after either but I did purloin one for a screen name.