Definition of Iman

Assalamu alaikum,

I heard somewhere (i forget where) that the meaning of a root of the word "Iman", which I think is A-Ma-Na (or mayber Aa-Man-na) means to confirm.

So actualy the things we have Iman in are things we have confirmed for ourselves to be absolutely true. For example, we have Iman in Allah, so we have confirmed to be absolutely true the existence of Allah, and his Oneness, etc.

Is this a correct definition?

I am just trying to reconcile this with the common definition of Iman, which is "Faith". The word "faith", I think commonly brings up the perception of things "we JUST believe in", "just because".

Unfortunately some Muslims I have met believe that Islam is a religion we follow "just because", and that most likely it is correct, but there is a possibility that it is wrong.

Please comment if you are informed on this issue.

And Allah Knows Best.