An Etymological Dictionary of the German Language/Annotated/frieren

frieren, verb, ‘to freeze, feel cold, be chilled,’ from the equivalent Middle High German vriesen (participle, gevrorn), Old High German friosan (participle gifroran); the change of s into r has obtained in all parts of the verb, yet s has been preserved in Frieseln and Frost. Compare Dutch vriezen, Anglo-Saxon freósan, English to freeze, Old Icelandic frjósa; Gothic *friusan is wanting, but may be inferred with certainty from frius, neuter, ‘frost, cold.’ The change of s into r is also shown by Anglo-Saxon freórig, adjective, ‘freezing, frosty, stiff,’ Old Icelandic frer, neuter plural, ‘frost, cold.’ The Teutonic root is freus, fruz, from the pre-Teutonic root preus, prū̆s. It appears to lie at the base of Latin prûrio for *prusio, ‘to itch,’ if the connecting link in meaning is to be found in the ‘piercing, itching, burning nature of frost.’ Old Indian has a root pruš, ‘to inject a substance,’ which is more remote in meaning; akin to Latin pruîna, ‘rime’ (for *prusvîna); Sanscrit prušvá, ‘drop, frozen drop, rime.’ Under no circumstances can the word be connected with Latin frigere.