To make happy or to fill with happiness; an archaic or poetic way to express bringing joy to someone.
From en- (prefix meaning 'to cause') + happy (from Old Norse happ, meaning 'chance' or 'fortune'). It's a rarely used verb form from Middle English combining the prefix with the adjective.
In older poetry and literature, 'enhappy' was used the way we might say 'make happy' today—it's the kind of romantic, heightened language you'd find in Shakespeare expressing the idea of filling someone with joy.
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