There are about three million people with the name Smith in the US. Figure another million or so in other English-speaking countries, a quarter of which have Gmail accounts (might be an underestimation; there are more than 400 million Gmail users), and you're left with a million Smiths using Gmail. How many of them tried that username format? I have no idea, but since there are only 676 possible strings of two Roman letters, it'd have to be less than one in a thousand and change. (Gmail addresses are not case sensitive.) Not holding my breath, in other words.

You might have better luck playing with . breaks between words. I've got the Gmail account firstname.lastname@gmail.com, although I'm blessed with an uncommon surname.