Once I was in a store here in Mexico and the clerk asked me if I wanted a “canastilla”. I didn’t know what she meant until she brought me a plastic shopping basket. My Mexican friends laughed when I said that I would have understood “canastita”. I still don’t know a rule for when to use -illa. I do know that “ventanilla” is the word for the small airplane window so I’m guessing that in general the “-illa” suffix is used for physically small things and not for any of the other uses.
But the suffix -it@ is used a lot. “Cafecito” is a common word and there are even restaurants that are named “El Cafecito”. A Spanish teacher once told me that the Mexicans used to use diminutives in order to set themselves apart from the Conquistadores, who made demanding, forceful requests.
