1340, "lucky," from
hap "chance, fortune" (see
haphazard), sense of "very glad" first recorded c.1390. Ousted O.E.
eadig (from
ead "wealth, riches") and
gesælig, which has become
silly. O.E.
bliðe "happy" survives as
blithe. From Gk. to Ir., a great majority of the European words for "happy" at first meant "lucky." An exception is Welsh, where the word used first meant "wise." Used in World War II and after as a suffix (e.g.
bomb-happy, flak-happy) expressing "dazed or frazzled from stress."
Happiness is first recorded 1530.
Happy hour "early evening period of discount drinks and free hors-d'oeuvres at a bar" is first recorded 1961.
Happy-go-lucky is from 1672.
Happy as a clam (1636) was originally
happy as a clam in the mud at high tide, when it can't be dug up and eaten.