Why do the Priest Wear their Collar Backwards

A little boy got on a bus and sat near a man reading  a book. And noticed that the mans collar was backwards ! He asks the man why he had worn it backwards to which the man replied” I am a Father” . The boy replied my dad does not wear it like that ! The priest looked up from his book and said.  “I am the Father of many “.  The little boy said my dad has 4 boys and 4 girls and 2 grandchildren and he does not wear his collar like that !!  The priest getting impatient said ” I am the Father of hundreds ” and went back to reading his book.  The boy sat quietly thinking a while,  then suddenly he leaned over and told the man.                       ” You should use condoms and maybe wear your pants backwards instead of your collar !!