Well, I'd like to ask about your experiences in naming your projects :)

And I have two questions

I've got a nice title for one of my ideas but the name has 5 words.

Is it too much for casual style game?

And for my another idea the perfect title is title of one song

Game is not related at all to that music - no theme, no representation of lyrics in that song - nothing just a title.

Can I do so or titles are copywrighted too? Title is a common words, no names etc

Both questions would be easier to answer if you'd tell us the actual title(and what the game is about).

I guess in general copyright people don't care about smaller projects, but it can become weird pretty fast (eg. elder scrolls vs notch).

If the title sounds nice and fits the game it doesn't really matter if its 5 words or just one.

Can't you really share the name suggestion with us? If you are releasing a game under that name and you don't want to speak about it here I think you already know the name is bad.

A quick tip about naming: google it. If you get results that you cannot top then better come up with different one.

Also consider the length only in this respect. If you have 1-2 word name then chances are someone has already named something identically and you have to compete about it. If you have 5 word name and it's identical to name of another thing it will seem like you are actually trying to make it related. Don't do it. Change 1-2 words out of 5 a bit. If the 5 word name is unique, interesting and meaningful to your game then by all means use it.

My advice is you will want a unique name. You might not yet have it but you will if you put your mind to it.

You can always just use a working title for a project. I feel that names emerge pretty organically during the process of development. You will truly understand why a game should be named something once you know exactly what you are making. You can't make a name that will stick from the very beginning. Like everything in game development it takes many iterations to get right.

Game titles can be copyrighted, I would come up with some alternatives in case you get into any legal trouble. The name needs to have some "characteristic" that makes it easy to remember and searchable. The length does not matter, take the title "I made a game with zombies in it". Pretty long and a bit unusual, still easy to remember!