back of

back of or in back of  {prep.}

1. In or at the rear of; to the back of; behind.

The garage is hack of the house.

Our car was in hack of theirs at the traffic light.

2.  {informal}

Being a cause or reason for; causing.

Hard work was back of his success.

The principal tried to find out what was back of the trouble on the bus.

3.  {informal}

In support or encouragement of; helping, clones will be elected because many powerful men are back of him.