How do I prevent my Mac from autocorrecting my username? Every time I try to login with my usual username (i.e. gsamaras), I get a pop-up, like a suggestion from my Mac, for the word samaras, so unless I click on the x button, "gsamaras" will be replaced by "samaras".

How can I tell my Mac not to correct gsamaras?

Note: Formatting the laptop is not an option.
Type your name, right click and pick "Learn Spelling".