Definition of "how come" [how come]

• Why; why is it; for what reason or purpose? (adverb)

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• "Which is how come Nick found himself sitting in Celtic Warrior in Nishi Azabu on a Thursday night, alone at the bar, nursing a bourbon and water and a headache, trying to maintain his sanity as a bad multiracial goth band played heavily Japanese-influenced Celtic war melodies, an assault on the ears almost too intense to be described, much less endured."
• "“So how come you and Sin hate each other?” she asked as Alan turned the car left at Alphington Junction."
• "And if he was, how come Joyful Turner was prepared to let him captain a fine sloop like Lisbetta?"