I came across the words 'insouciant' and 'blithe' in a random article two days ago. I don't remember what it's called. I looked the words up on Dictionary.com which gives the following. "1) Insouciant: free from concern, worry, or anxiety; carefree; nonchalant." "2) blithe1)without thought or regard; carefree; heedless:a blithe indifference to anyone's feelings.2)joyous, merry, or happy in disposition; glad; cheerful:Everyone loved her for her blithe spirit." Is there any difference in meanings between the words? I get the feeling both words have the common definition of 'careless or cheerful indifference that evokes signs of calmness and untroubledness'
Neither of these words is in common usage.
Google ngram's results for "Blithe" are dominated by the use of "Blithe" as a proper name, or reference to the play "Blithe Spirit". The word comes from Old English. It has deep roots in the language, but is hardly used anymore.
The frequency is much much less for insouciant. I cannot remember the last time I encountered it, and I read a lot of books. The word has a French origin, not English. So it is much more literary.
Because these are exceedingly rare words, it is very difficult to nail the differences.
Comments
The person is insouciant. You can't have an insouciant indifference. "Insouciant" is a close synonym of "carefree". "Blithe" is more like "uncaring" but in a breezy way, not callous. "Insouciant" is high register. "Blithe" is of even higher register verging on poetical except in some collocations like "blithe indifference". "Blithe" owes any currency it has to the famous poem "To a Skylark", by Shelley, which has the phrase "blithe spirit", which people unconsciously misquote, thinking this "spirit" is a person's character.