Nate gave a squeal of delight when Luke snatched him. After a short, furious battle, Luke let himself be pinned. He grunted with exaggerated bursts as Nate bounced on his stomach.
“You’re too tough for me, kid. Uncle.”
“Uncle who?”
“Just uncle.” Chuckling, Luke ruffled Nate’s dark hair. “It means I give up.”
Honest Illusions
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By SusanHanisch - Own work, CC BY-SA 4.0,
https://commons.wikimedia.org/w/index.php?curid=51448331
Anyone know where the phrase 'Say Uncle' meaning 'I give up' came from?