Baretti: A dictionary of the English and Italian languages
Assottigliá-re, v. a.
1. to fine down, make thin, taper off, sharpen; 2. to refine, render acute, teach finesse; v. n. 1. to diminish; 2. to be over-nice; v. r. 1. to sharpen one's intellects;2. to endeavour, try; s. m. Assottigliá-tóre, f. Assottigliá-tríce; adj.Assottigliá-nte .
Florio: a worlde of wordes, or most copious, dictionarie in Italian and English
assottigliare: to subtilise, to make small, thin, or slender. Also to weaken or empaire.