借りてきた猫 was translated as a borrowed cat. In that case, why 借りてきた is used instead of just 借りた猫? What additional meaning does it want to imply?
Good question! I had to think of the reason for a while.
I think きた of 借りてきた猫 emphasizes the fact that the cat has come "here" which is different from where it used to belong. The cat is now quite a stranger "here." It doesn't know what to do, and has to keep quiet and still.
借りた猫＝a borrowed cat
借りて来た猫＝a borrowed and coming to a new place cat