Odd man out noun
Everyone in the group considers Jake the odd man out.
I was always the odd man out at school.
If we divide our group into four there will be an odd man out.
Used to say someone is alone
This idiom was recorded in the mid 19th century; its earliest use was found in The Times.
If you fall for someone's trick the first time then they are at fault.
Are you going to mess with me again? Fool me once, shame on you; fool me twice, shame on me.