What is the Korean abbreviation 엄친아 short for?

• 엄격한 친구 아빠 (a friend's strict father)
• 엄마 친구 아들 (Mom's friend's son)
• 엄청 친절한 아이 (an extremely kind child)
• 엄마 친척 아저씨 (a man on Mom's side of the family)

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