blissful adj.

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. It has been influenced by unrelated bless.

word-forming element attached to nouns (and in modern English to verb stems) and meaning "full of, having, characterized by," also "amount or volume contained" (handful, bellyful); from Old English -full, -ful, which is full (adj.) become a suffix by being coalesced with a preceding noun, but originally a separate word. Cognate with German -voll, Old Norse -fullr, Danish -fuld. Most English -ful adjectives at one time or another had both passive ("full of x") and active ("causing x; full of occasion for x") senses.

It is rare in Old English and Middle English, where full was much more commonly attached at the head of a word (for example Old English fulbrecan "to violate," fulslean "to kill outright," fulripod "mature;" Middle English had ful-comen "attain (a state), realize (a truth)," ful-lasting "durability," ful-thriven "complete, perfect," etc.).