self.title sets navigationController and tabBarItem's title? Why?

I do this in a UIViewController for one of my tabs:

self.title = @"Welcome";

However, it's overwriting whatever I have for the tabBarItem. I have tried:

self.tabBarItem.title = @"Home";

and

[self.tabBarItem initWithTitle:@"Home" image:[UIImage imageNamed:@"iconHome.png"] tag:0];

But still, self.title overwrites the tabBarItem, regardless of whether I am trying the two latter pieces of code after the title has been set. The code even runs without errors, but the self.tabBarItem.title or initWithTitle doesn't do anything?