What is the origin of the phrase "Be still, my heart"?

Question

I'm not American or English, so I may be asking a silly question... However, I was wondering if there is a famous occurrence (or origin) of this phrase - such as, in a classic work of literature, movie, or something like that?

I kept wondering where I first heard this phrase...

Thanks!

Answer 1

It is from Homer. The original quote is "Be still my heart; thou hast known worse than this."