Hap
Middle English: from Old Norse happ .
wiktionary
From Middle English hap, happe(“chance, hap, luck, fortune”), from Old Norse happ(“hap, chance, good luck”), from Proto-Germanic *hampą(“convenience, happiness”), from Proto-Indo-European *kob-(“good fortune, prophecy; to bend, bow, fit in, work, succeed”). Cognate with Icelandic happ(“hap, chance, good luck”). Related also to Icelandic heppinn(“lucky, fortunate, happy”), Old Danish hap(“fortunate”), Old English ġehæp(“fit, convenient”), Swedish hampa(“to turn out”), Old Church Slavonic кобь(kobĭ, “fate”), Old Irish cob(“victory”).
The verb is from Middle English happen, from Old Norse *happa, *heppa, from Proto-Germanic *hampijaną(“to fit in, be fitting”), from the noun. Cognate with Old Danish happe(“to chance, happen”), Norwegian heppa(“to occur, happen”).
From Old English hap.
Shortening of Haplochromis
etymonline
hap (n.)
c. 1200, "chance, a person's luck, fortune, fate;" also "unforeseen occurrence," from Old Norse happ "chance, good luck," from Proto-Germanic *hap- (source of Old English gehæp "convenient, fit"), from PIE *kob- "to suit, fit, succeed" (source also of Sanskrit kob "good omen; congratulations, good wishes," Old Irish cob "victory," Norwegian heppa "lucky, favorable, propitious," Old Church Slavonic kobu "fate, foreboding, omen"). Meaning "good fortune" in English is from early 13c. Old Norse seems to have had the word only in positive senses.
hap (v.)
"to come to pass, be the case," c. 1300, from hap (n.) "chance, fortune, luck, fate," or from Old English hæppan.
