Does it contradict the prophethood of Muhammad (peace be upon him) to know the name "Muhammad" before his birth, and the claim of some Muslims that he was the first to be named by it?

The claim that the Prophet is a liar because his name is Muhammad is incorrect, as Allah did not state that he was the first to be named by this name, nor did the Prophet say that about himself. The misinformation circulated by some people regarding this matter does not affect the religion.

Allah inspired the Arabs to name him Muhammad due to the praiseworthy qualities he possessed that were consistent with the name. And Abdul Muttalib named him Muhammad out of a desire for Allah and His creation to praise him.

None of those who bore this name before him claimed prophethood. Moreover, Allah protected against anyone being named by this name before him, except in very rare instances, in order to eliminate doubt and suspicion. He also protected everyone named by it after him from claiming prophethood, so that he alone would remain unique in it.