bliss (n.)

Old English blis, also bliðs "bliss, merriment, happiness, grace, favor," from Proto-Germanic *blithsjo (source also of Old Saxon blidsea, blizza), from *blithiz "gentle, kind" (see blithe) + *-tjo noun suffix. Originally mostly of earthly happiness, in later Old English of spiritual joy, perfect felicity, the joy of heaven; influenced by association with unrelated bless.

often with out, by 1973, U.S. colloquial, from bliss (n.).