A lot of commonly-accepted abbreviations exist only because a critical mass of people use them. We understand what “btn” means because we’ve seen it before, not because it’s a clear shortening of “button.”
Is the loss of clarity outweighed by the benefits of a shorter class name? In an era where most text editors provide autocompletion, three letters isn’t a huge difference from an authoring perspective.
Inevitably, someone else will come along someday and work with the code we write. Even if you work by yourself, future you will be a different person because of the work you’ve done and the experiences you’ve had between the times you focus on a project. Clarity is invaluable when others (or our future selves) come in to work on something—we don’t have to struggle to understand what is happening, we can get work done more efficiently, and the overall process will be much smoother.
There are clearly good reasons for both approaches, so like most things in our work, it all comes down to how you decide what’s right for you and your situation. Is there a tangible, data-proven benefit of brevity? If not, be descriptive, expressive, and clear.
No matter what, avoid abbreviating for abbreviation’s sake. The benefits of clear, readable code are almost always greater than typing fewer characters. And if brevity is applied thoughtfully in technical situations, you’ll use resources more efficiently, and that will make everyone happy.