How is “so help me” used?

In How the West Was Won (1962), one line is: “...and so help me, the bucket was full of rocks.”

Which movie is “so help me” from?

The clip at the top of this page is from How the West Was Won (1962).

...and so help me, the bucket was full of rocks.

8 作品で登場 · 1 本目

used to swear that what you are saying is true, especially in a court of law

49 本の映画に登場

オックスフォード映画の 100%
used to swear that what you are saying is true, especially in a court of law
So help me God.
It sounds crazy, Keyes, but it's true, so help me.

定義：Oxford Advanced Learner's Dictionary 第 9 版