Who named our prophet 'Muhammad' and why?

This is actually my son's question but I could not find a satisfactory quick answer. The meaning from the derived Arabic root H-M-D (to praise) is praiseworthy, commendable, laudable. src I am assuming his parents gave him this name, but his birth was 40 years before his call to prophet hood. How did his parents know he would be praiseworthy? But the 'praiseworthy' meaning would not be correct since all praise belongs to Allah. The first aya of the first sura says 'Al Hamdu Lilahi Rabil Alameen' 'Praise be Allah, the Lord of the Worlds' By the age of 6, he was orphaned after both his parents died. Did he have a different name at birth, and changed after adoption into his uncle Abu Talib's family? This could be a possibility since he might have shown uniquely praiseworthy behaviors even in his first six years. If we look it previous prophets, some had unique names but others had common names. For example, Musa (hebrew: Moshe) means 'come out of water' in reference to his being found in a floating cradle in the Nile. It is a unique name. In contrast Isa (ibn Meryem) commonly known as 'Jesus' original Aramaic name is 'Yeshua' (Joshua in English) was a common name among the bani Israel at that time. According to my understanding the name 'Muhammad' was not common among the Arab tribes at that time. The seera says the name Muhammad was assigned by Allah. But this is vague since all things come from Allah. How was this name assigned to him? I am sorry if I am asking a question with a simple and obvious answer.