what's the meaning of "give me five"

[ananda 1]

often heard of this phrase, but what's the exactly meaning?

why not 'give me three'?

[skylee 1,912]

高興的時候邀請對方互相擊掌時說 : "Give me five." (Imagine 擊掌為誓 but drop the "為誓" part)

Five because your hand has five fingers.

[ananda 1]

thanks, but some people have six fingers

[skylee 1,912]

Actually, most people have four fingers and one thumb on each hand.