Where does that come from?

At school, Rachel learned about the expression "where does that come from"
Where does milk come from --from cows
Where do eggs come from --from hens
When she was asked where French fries do come from, she simply replied from France, which is quite logical to me.

Rachel loves her new school and is very happy there.
She missed 2 days last week since she has developed a bad cough which will be over soon hopefully.
Where did that one come from, I wish I knew...