It probably comes from an expression used for many years by people who fix parts of cars and trucks.

VOA: special.2009.11.29

Speaking of personal questions, there is an expression people sometimes use when their children ask, "where do babies come from?"

VOA: special.2009.06.28

But there is an expression to get cold feet that has nothing to do with cold or your feet.

VOA: special.2009.12.13

This is also an expression used to show a feeling like surprise or disappointment.

VOA: special.2010.02.07

Throwing cold water also is an expression that deals with ideas or proposals.

VOA: special.2009.05.10

A brown out is an expression for a reduction in electric power.

VOA: special.2009.11.15

Water over the dam is an expression about a past event.

VOA: special.2009.05.10

In fact,there is an expression "easy come,easy go" that recognizes this.

VOA: special.2010.08.29

Joe Blow is also an expression for a common man.

VOA: special.2010.02.07

Out in the cold is an expression often heard.

VOA: special.2009.12.13

There is an expression for this,too.

VOA: special.2010.06.20

Among the flower arrangements is an expression of sympathy with the Kyrgyz people from the Talas Gold Mining Company.

VOA: standard.2010.04.15

It is cut to the chase. She heard that expression when she attended an important meeting of one company.

VOA: special.2010.07.25

I did not know she was married!" Language expert Webb Garrison tells an interesting story about the expression.

VOA: special.2010.02.14