In the United States and Canada, the idiomatic expression "Say 'uncle'!" may be used as an imperative command to demand submission of one's opponent, such as during an informal wrestling match or tickling. Similarly, the exclamation "Uncle!" is an indication of submission - analogous to "I give up" - or it may be a cry for mercy, in such a game or match. An expression of surprise or disbelief.
The word comes from Latin: avunculus the diminutive of avus "grandfather" and is a family relationship within an extended or ... 1. a brother of one's father or mother 2.