This guy with a age gap keeps calling me 'my daughter'?

He's 9 years older than me and I told him I couldnt date him because of that age gap so we remained friends even tho he didn't see no issue with it. Now he calls me my daughter from time to time jokinly and I just laugh it off but find it lowkey weird?
This guy with a age gap keeps calling me 'my daughter'?
Post Opinion