If you refer to Arabic language dictionaries you will find out that the meaning of the word Islam is: submission, humbling oneself, and obeying commands and heeding prohibitions without objection, sincerely worshiping Allaah alone, believing what He tells us and having faith in Him. The word Islam has become the name of the religion which was brought by Muhammad (peace and blessings of Allaah be upon him).
All the religions on earth are called by various names, either the name of a specific man or a specific nation. So Christianity takes its name from Christ; Buddhism takes its name from its founder, the Buddha; the Zoroastrians became well known by this name because their founder and standard-bearer was Zoroaster. Similarly, Judaism took its name from a tribe known as Yehudah (Judah), so it became known as Judaism. And so on. Except for Islam, for it is not attributed to any specific man or to any specific nation, rather its name refers to the meaning of the word Islam. What this name indicates is that the establishment and founding of this religion was not the work of one particular man and that it is not only for one particular nation to the exclusion of all others. Rather its aim is give the attribute implied by the word Islam to all the peoples of the earth. So everyone who acquires this attribute, whether he is from the past or the present, is a Muslim, and everyone who acquires this attribute in the future will also be a Muslim.