プログレッシブ和英中辞典(第4版)の解説
あいがん【哀願】
an appeal ((to a person; for a thing))；《文》 an entreaty, (a) supplication ((for))
哀願する appeal ((to a person to do; for a thing))；《文》 entreat [implore] ((a person (to do); for a thing))；plead ((with a person 「for a thing [to do]))
私は彼に慈悲を［助けてくれるように］哀願した
I entreated [implored/pleaded with] him 「for mercy [to help me].