Nonchalant. It's a very common word and its present meaning varies only slightly from the original.
"Non-" is classified as a prefix which, of course, means that is affixed to the beginning of words, bases, and phrases. Just tacking a “non-” onto the front of some letters doesn’t mold them into a word. There needs to be a preexisting word there for “non-” to be effective.
Chalant would make an ideal word if it were to be reintroduced into our lexicon. Its possible interpretations vary. The Old French “chaloir” could be used as a more chimerical version of “worry,” or “fret.” The Latin form-”calere”- is even better. There are three definitions for it. The first being: “to be warm,” the second: “to be troubled” is good, too. But the third definition: “to be warm, inflamed with desire” is amazing.
If for no other reason, I would like to see chalant become a word just so I can hear this is a porno: “Oh...oh yeah. Baby, you got me all chalant bothered!”
See?! Chalant needs to be a word! Its potential is far too great for it not to be included into our language.
Facts provided by:
http://www.dictionary.com/cgi-bin/dict.pl?term=nonchalant
Merriam Webster’s Collegiate Dictionary, Tenth Edition.