verb

• (intransitive) To occur or take place.
  "Let me tell you how it happened."
• (transitive, archaic) To happen to; to befall.
  "'By my soul! I believe something bad has happened me,' he muttered, and popped up his window, and looked out, half dreaming over the church-yard on the park beyond […]"
• (intransitive or impersonal, with infinitive) To do or occur by chance or unexpectedly.
  "Take an umbrella in case it happens to rain."
• (followed by on or upon) To encounter by chance.
  "Unexpectedly, in a nook close by the farmhouse, he happened upon a spot where the vintage had actually commenced."

adv

• (obsolete or dialect) maybe, perhaps.
  "Yeah, well happen if he'd gone quietly, she wouldn't have needed to show him who's in charge."