Islam and Muslim are both Arabic words that are derived from three letters: seen laam and meem, س ل م. These three letters make up the root word, selima, which, when the letters are rearranged, has a multitude of meanings from providing safety to sincerity.
Selima in its original form means to be safe, secure, protected, guarded or free from. The Prophet (peace and blessings be upon him) used the word selima to describe a Muslim. He is reported to have said "A true Muslim (person who surrenders to God) is he from whose tongue and hand other believers remain safe (selima).” (1) Here, the word selima is being used to describe one of the attributes of a true Muslim, which is someone who keeps from harming others.