blithe

Concise Oxford English Dictionary © 2008 Oxford University Press:
blithe /blʌɪð/

▶adjective

• 1 cheerfully or thoughtlessly indifferent.

• 2 literary happy or joyous.

– derivatives
blithely adverb,
blitheness noun,
blithesome /-s(ə)m/ adjective (literary).

– origin OE blīthe, of Gmc origin; rel. to bliss.