Why do girls like boys with "Big" s?

i am a teenager and I have kind of a "big" (Afraid to go to jail because of this) And @ school girls are always making comments like "Big boi" and im feeling VERY un comfortable when I hear this I try to ignore this but like every other day theres a comment about my And I overhear them speaking about it saying things like "He has a nice ***" it's very very, unusual, can someone please tell me why some girls "Like" Guys with big s? Because I dont understand it