An act of entreating: Plea. (Merriam – Webster)
An attempt to persuade someone to do something: (Cambridge Dictionary)
Earnest request or petition; supplication. (Dictionary.com)
An earnest or humble request. (Oxford Dictionaries)
An entreaty is a very polite, serious request. (Collins Dictionary)
Entreaty. Clip Art.
A song of entreaty. Church of England.