An Etymological Dictionary of the German Language/Annotated/Schlag
Schlag (1.), masculine, ‘sort, race, family, class’; see Geschlecht.
Schlag (2.), masculine, ‘stroke, blow,’ from the equivalent Middle High German slac (genitive slages), Old High German slag, masculine; a verbal abstract of the root slah, ‘to strike.’ Modern High German schlagen, ‘to strike, beat, pulsate,’ Middle High German slahen, Old High German slahan, ‘to strike’; the g of the Modern High German verb is due to the grammatical change of h to g. Compare Gothic slahan, Old Icelandic slá (also ‘to mow down’), Anglo-Saxon sleán (from sleahan), English to slay, Dutch slaan, Old Saxon slahan, ‘to strike.’ Teutonic root slah (slag), from pre-Teutonic slā̆k; akin to Greek λακίζω, Latin lacerare, ‘to tear to pieces or rags,’ for slak-?. A root similar in sound appears in Old Irish slechtaim, sligim, ‘I strike’ (root sleg). See Geschlecht and schlau.