This is the 59th most frequent Arabic word.
عليه
Upon him / On him
In this sentence, 'عليه' means 'on him' and is part of the phrase that indicates reliance or dependence upon someone.
اعتمدنا عليه في إنجاز المشروع.
We relied on him for completing the project.
'عليه' here indicates an obligation or duty assigned to the person.
كان عليه أن ينظف الغرفة قبل خروجنا.
He was supposed to clean the room before we left.
Here, 'عليه' is used to mark the subject of blame or responsibility.