An Etymological Dictionary of the German Language/Schweiß
Schweiß, m., ‘sweat, perspiration,’ from the equiv. MidHG. and OHG. sweiȥ, m.; MidHG. also ‘blood,’ a meaning still current among sportsmen (so too schweißen, ‘to bleed’); OSax. swêt, ‘sweat,’ AS. swât, ‘sweat, blood,’ E. sweat, Du. zweet. For the Teut. root swī̆t, swait, Aryan swoid, swī̆d, see under schwißen; comp. Sans. svẽda-s, m., Lat. sudor (from *svoidos), ‘sweat.’ To this is allied schweißen, vb., ‘to begin to melt, weld,’ from MidHG. sweiȥen, sweitzen, ‘to weld, OHG. sweiȥen, ‘to roast, broil.’