Buenchico, the '-et' is a diminutive, the same as the '-y' in 'beaky'. But diminutive doesn't always imply 'small size', it's also used in creating a more 'familiar' version of the word (like Harry for Henry). So you might call someone Fatty, Skinny, Shorty, Lanky and so forth: you're drawing attention to a physical characteristic without necessarily meaning the people themselves are small.
(Well, except for Shorty, I suppose.)
There's some discussion of it here:
http://books.google.c...ket%20surname&f=false