Meanings of the word 'Islam'

The root of the word ISLAM is S-L-M, which has the following meanings [according to dictionaries]:

-Submission and obedience (to Allah)
-Humility, submissiveness and conformance (to the Laws of Allah)
-Safety, security, immunity or freedom from evil or affliction of any kind
-Peace

Al-Islam is a way of life whereby one takes upon oneself what Allah Has ordained and His Messenger practically demonstrated and conveyed to the mankind. It entails total submission and obedience to Allah that leads one to  peace, and safety, security, immunity and freedom from evils and afflictions of any kind form within or without.

The meaning of the word 'islam' have been further elaborated in the Quran

Muslimeen vs. Mujrimeen

In 68:35 the word Muslimeen has been used in contrast to Mujrimeen. Mujrim is the one who commits an act of disobedience or violates the Law. So Muslim is the one who does not commit any act of disobedience to Allah or does not violate the Divine Law.

Muslimoon vs. Qasitoon

In 72:14, the word Muslimoon has been used in contrast to Qasitoon. Qasitoon are those who deviate or decline from the right course; who act unjustly, injuriously, wrongfully or tyrannically. So Muslimoon are those who always keep on the right course as prescribed by Allah and always act justly and rightfully.

Muslimeen vs. the arrogant

In 27:31, the word Muslimeen has been used in contrast to "the arrogant". So a Muslim is the one who is not arrogant but submits himself to the Laws of Allah

Muslim and Momin

Allah distinguishes "Muslim" from "Momin" [33:35, 66:5]. The one who believes in the Divine Law, is a believer [i.e. a Momin]. The one who conceals or rejects the Divine Law, is a non-believer or KAAFIR. The one who submits himself to the Divine Law and lives according to it, is a Muslim. The one who violates the Divine Laws is a Mujrim, or arrogant or deviator from the right path.
Just being a Momin is not enough. Allah Wants us to be Momin as well as Muslim i.e. a Believer in the Divine Laws as well as a Submitter to these Laws. According to 43:69, those who will qualify to enter Paradise will be Momins as well as Muslims i.e. they will not only believe in the Divine Laws but also abide by these Laws. According to 49:14, one is not qualified to consider himself Momin until he is a true believer from the heart even if he submits or surrender himself to the Laws of Allah.

The name 'Muslimeen' is given by Allah

According to 22:78, Allah has named us MUSLIMEEN yet we call ourselves Sunnis, Shias, Brelvis, Ahl-e-hadith etc. It is not only us whom Allah has named as MUSLIMEEN but also those who came before us and vowed to submit to Allah's Laws were also named MUSLIMEEN. But they, later on, changed their names and became "Jews" and "Christians".

[22:78] …He is the one who named you "MUSLIMEEN"…

Islam before Muhammad [p.b.u.h]

Islam did not come into being after the revelation to Muhammad [p.b.u.h] but it existed before the life of Muhammad [p.b.u.h]

Ibrahim [p.b.u.h] and Ismael [p.b.u.h] prayed to Allah to become Muslims [2:128]

[2:128] "Our Lord, make us Muslims [i.e. submitters] to You, and from our descendants let there be a community of Muslims [i.e. submitters] to You."

When Allah commanded Ibrahim [p.b.u.h] to submit [i.e. become a Muslim], he submitted [and became a Muslim] [2:131]

Ibrahim, Ismael, Ishaaq and Jacob were all Muslims [2:132-133, 3:67]

Another name of Jacob [p.b.u.h] was ISRAEL. So all Israelites were originally Muslims then deviated from the right path

The Companions of Jesus Christ were all Muslims [3:52, 5:111]

Muhammad [p.b.u.h] was commanded to be a Muslim [i.e. Submitter]

[6:163] "He has no partner. This is what I am commanded to believe, and I am the first to submit [ or embrace Islam]."

[10:72] I have been commanded to be a submitter [i.e. a Muslim]

[27:91…I am commanded to be a submitter [i.e. a Muslim]

[39:12] "And I am commanded to be the first and the foremost submitter [i.e. a Muslim]."

[40:66] …I was commanded to submit [i.e. to embrace Islam] to the Lord of the universe

The only religion Deen approved by Allah is ISLAAM [3:19, 5:3]

[21:108] Say: "What has come to me by inspiration is that your Allah is One Allah: will ye therefore become Muslims?"

[2:208] "O you who believe, you shall embrace total submission…"

[31:22] "Whoever submits his whole self to Allah, and is a doer of good, has grasped indeed the most trustworthy hand-hold"

In 2:112, one of the outcomes of Submission to Allah is given as follows:

[2:112] "Indeed, who submit themselves to Allah and are the doer of the good, they will get their reward from their Lord and they will have nothing to fear nor will they grieve"