Originally meant 'lucky,' from Old Norse 'happ' (chance) — the emotional sense came later; kin to 'happen' and 'mishap.'
Feeling or showing pleasure or contentment.
From Middle English 'happy' (fortunate, lucky), from 'hap' (luck, fortune), from Old Norse 'happ' (luck, chance), from Proto-Germanic *hampą, possibly from PIE *kob- ('to suit, to fit, to succeed'). The original meaning was entirely about luck and fortune, not internal emotional state—a 'happy' person was a lucky one. The semantic shift from 'fortunate' to 'feeling pleasure' occurred gradually during the 14th–16th centuries, paralleling a broader cultural movement toward internalising emotional vocabulary. Compare the similar
'Happy,' 'happen,' 'perhaps,' 'mishap,' 'haphazard,' and 'hapless' all come from Old Norse 'happ' (luck). Something that 'happens' occurs by chance. 'Perhaps' means 'by luck.' A 'mishap' is bad luck. 'Haphazard' is chance + chance. And 'hapless' means 'luckless.' Happiness was originally about fortune, not feelings.