The etymology may play a role here:
Flotilla goes way back to Indo-German times:http://www.merriam-webster.com/dictionary/flotilla
Etymology: Spanish, diminutive of flota fleet, from Old French flote, from Old Norse floti; akin to Old English flota ship, fleet http://education.yahoo.com/reference/dictiona...
Spanish, diminutive of flota, fleet, from Old French flote, from Old Norse floti; see pleu- in Indo-European roots
Tortilla, on the other hand, has no such origins and seems to be a term indigenous in the Spanish language only.http://en.wikipedia.org/wiki/Corn_tortilla
Tortilla, from Spanish Torta, cake, plus the diminutive -illa, literally means "Little cake".http://www.allwords.com/word-tortilla.html
Etymology: From Spanish for a small flat round bread or pancake in Mexico. In Spain a tortilla is an omelette but a torta can be a sort of fried pancake.