An Etymological Dictionary of the German Language/Siegel
Siegel, n., ‘seal, signet,’ from the equiv. late MidHG. sigel, m. (wanting in OHG.); in the classical period MidHG. insigel, insigele, OHG. insigili, n. It cannot be determined whether MidHG. sigel, which was substituted for the latter term, was borrowed at a later period from Lat. sigillum, or whether it was formed again from MidHG. besigelen (OHG. bisigelen), ‘to seal,’ and entsigelen (OHG. intsigilen), ‘to unseal’; nor is it known how OHG. insigili is related to Lat. sigillum. In Goth. a term sigljô, n., occurs.