Mohammed is one English spelling of a very famous Arabic name. It is the name of the Prophet who founded the religion of Islam, and it is also a common man's given name among Muslims. Other English spellings you will see are Muhammad, now the most usual in careful writing, and, in old books, Mahomet. The Arabic name is generally taken to mean “praised” or “worthy of praise”. In English, when you write about a living person, follow the spelling they use for themselves. For the Prophet, many newspapers now prefer Muhammad, but Mohammed is still widely used and is not a “wrong” word — it is one of the older European spellings. Say the name with respect; it is not a casual nickname. Muslims honour him as a prophet and messenger, not as God.