FAO Spanish speakers...

[Griff]

cf: ampollas (Sp): ampoules (Eng/Fr): ampulla (Latin). Taking it a bit further, it could also mean a bulb (eg light bulb or bulb of a thermometer. The latin "ampulla" means a flask or bottle. The "-ulla" ending normally indicates a diminutive form of a noun, therefore it could be a small "amphora".

Anyway, that's enough etymology for this morning! You were probably thinking "blisters" all along.