Although it is a noun, supplication comes from the Latin verb supplicare, which means "to plead humbly." While a supplication is often thought of as a religious prayer (it is used 60 times in the Bible), it can logically be applied to any situation in which you must entreat someone in power for help or a favor. 

The word supplication was first used in English during the Middle English period (1150–1500). The earliest known use of the word was in the writing of John Gower, a poet, before 1393. 

Examples of supplication in a sentence: 
"He fell to his knees in supplication"

1 hour ago, Bill W said:

Although it is a noun, supplication comes from the Latin verb supplicare, which means "to plead humbly." While a supplication is often thought of as a religious prayer (it is used 60 times in the Bible)

I am actually surprised that supplication is used so infrequently in the bible, considering that the bible consists of 66 books (73 for the catholic bible) and running to over 780k words of highly religious text. But, I'm pleased that I keep learning new things through this blog.

Just the facts:

https://www.merriam-webster.com/dictionary/supplicate

SUPPLICATION Synonyms: 19 Similar Words | Merriam-Webster Thesaurus