...we understand the same thing under the term "nickname".
If I undrestand correctly, to you it is something a person is getting called all the time. I find it more... well, something you don't call a person constantly. I agree it would be disgusting (though I have seen similar situations in real life) to call
Violet all the time
Viola, but I can easily imagine someone calling
Violet Viola from time to time. Those names have completely different auras, and in romantic-shakespearian mood I'd propably use
Viola instead of
Violet.