An Etymological Dictionary of the German Language/Annotated/Sinau
Sinau, masculine, ‘lady's mantle’; the earlier Modern High German variants Sindau and Sindawe point to Middle High German and Old High German *sintou, whose literally sense, ‘ever-dew’ (see Singrün), characterises the plant more simply than the terms Taubehalt, literally ‘dew-holder,’ and Tanschlüssel, literally ‘dew-key,’ which are applied to it.