An Etymological Dictionary of the German Language/Annotated/seichen
seichen, verb, ‘to make water,’ from the equivalent Middle High German seichen, Old High German seihhen; allied to Modern High German Seiche, ‘urine,’ and the equivalent Middle High German seiche, feminine, seich, masculine, Old High German seih, masculine; Gothic *saiqjan, ‘to make water,’ is wanting; with these sickern, ‘to ooze,’ and Low German sêken, ‘to make water’ (Teutonic root saik, saiq), are connected. The Aryan root sī̆q, mentioned under seihen, appears in Old Slovenian as sĭcati, with the same meaning, ‘to make water’; compare Old Slovenian sĭcĭ, masculine, ‘urine.’