An Etymological Dictionary of the German Language/Annotated/schwitzen
schwitzen, verb, ‘to sweat, perspire,’ from the equivalent Middle High German switzen, Old High German swizzen; Gothic *switjan is wanting. The Teutonic root swī̆t, Aryan swī̆d, is primitively Aryan, as was observed under Schweiß (a common Aryan root for ‘to freeze’ is wanting; compare Winter, Schnee, frieren, and Sommer); compare Sanscrit svidyâ-mi, from the root svid, ‘to perspire,’ Greek ίδίω, ‘I perspire,’ ἱδρώς, ‘perspiration,’ for σϝϊδ-, and further Latin sûdare, ‘to perspire’ (for *swoidare), Lettic swidrs, ‘perspiration.’