purgo.

Disputed. According to De Vaan, the term probably derives from Proto-Italic *pūr (“fire”) + agō (“to do”). The term would have originally meant "to lead the fire about," whence "to purify." The linguist Gregory Nagy posits a pre-form of the shape *pūrigō, which is marked by the suffix -igō. Regarding the sense development, Nagy suggests that the verb originally meant something such as "to activate, do fire," which perhaps parallels the usage of Umbrian 𐌀𐌇𐌕𐌉𐌌𐌄𐌌 (ahtimem, “fire-brazier(?)”) in a fire-ritual. Moreover, he compares the semantics Latin fumigō (“to smoke, fumigate”), which derives from fūmus (“smoke”) + -igō, and thus presumably evolved from a literal meaning of "to do smoke" to "to smoke, fumigate." Schrijver alternatively suggests that the term derives from earlier *pūrigō, *pūrigāre, itself from pūrus (“pure”). De Vaan, however, argues that a compound *pūro-agō- should produce a form with a medial long-vowel.