why do most Muslims have "Hussein" or "Muhammad" or some derivative of the name? It seems quite confusing.

Muhammad refer to the prophet of Islam. you also will hear people their name is ISA (Jesus) or any other prophet Name. as they believe no prophet is any mean part of God and all prophets are human beings.

Hussein is the grandson of Muhammad. and mostly Muslims-Shia use this name the most. because in some part of a history they were close to Hussein and follow alot of his teaching.

:}

Mohammad was their prophet and Hussein was his grandson .

all Islamic people tend to like to choose the prophets name for their children. Hussein was a grandson and an Imam, Shiite's and twelvers tend to also select that name cor their children. They do it in the same way that many Christians select biblical names. Interesting I have never met a Muslim with the name Isa are there any or many?

It's for them to have the goodies from the original person with the name. It's religious thing.

Maybe your answer is why the names are all the same?

Maybe it's beacuse there aren't too many blessed people nowadays.

i believe you can answered your question