Baretti: A dictionary of the English and Italian languages
Stemperáre, v. a.
1. to mix a solid with a liquid, to dilute, temper, dissolve; 2. to soften, allay;3. to soften a piece of tempered steel, to spoil the temper of a sword, &c., to blunt, dull; 4. to remove or change the temperature; v. n. 1. to dissolve, corrupt, spoil; 2. (fig.) to become corrupt (as a language); 3. to lose its temperature.
Florio: a worlde of wordes, or most copious, dictionarie in Italian and English