An Etymological Dictionary of the German Language/Annotated/Siegel

Siegel, neuter, ‘seal, signet,’ from the equivalent late Middle High German sigel, masculine (wanting in Old High German); in the classical period Middle High German insigel, insigele, Old High German insigili, neuter. It cannot be determined whether Middle High German sigel, which was substituted for the latter term, was borrowed at a later period from Latin sigillum, or whether it was formed again from Middle High German besigelen (Old High German bisigelen), ‘to seal,’ and entsigelen (Old High German intsigilen), ‘to unseal’; nor is it known how Old High German insigili is related to Latin sigillum. In Gothic a term sigljô, neuter, occurs.