*pops out of nowhere*
"Chara" is likely short for "Character," as all internal references of either Frisk (mainchara) or Chara (truechara) use "chara."
"Chara" (χαρά) in Greek means "joy," "delight," or "gladness."
"Cara" is the Irish word for "friend."
"Xará" is slang for "buddy" or a person with the same name as you and "Cara" can mean "dude" or "face" in various languages.
"Kara" (空) is a Japanese word meaning "empty", possibly referring to Chara's eyes.
"Chara" (חרא) as pronounced in Hebrew is considered an insult that means deification/feces/excrement, possibly referring to the corrupted, ill-tempered genocidal nature of Chara in the Genocide Route.
Chara is the second-brightest star in the constellation Canes Venatici.
The name "Chara" may also be based off the English word "char," meaning to leave something burnt.