Meaning

verb come to pass

verb happen, occur, or be the case in the course of events or by chance; ; (Santayana)

verb chance to be or do something, without intention or causation

originFrom Middle English happenen, hapnen, augmented from Middle English happen (“to come to pass, happen”), perhaps from Old English hæppan (“to move accidentally, slip”) and/or from Old Norse *happa, *heppa, from Proto-Germanic *hampijaną (“to fit in, be fitting”). Equivalent to hap (“a chance, occurrence, byfall”) + -en (verbal suffix).

Etymology from Wiktionary, CC BY-SA 3.0