Old English us (cognate with Old Saxon, Old Frisian us, Old Norse, Swedish oss, Dutch ons, German uns), accusative and dative plural of we, from PIE *nes- (2), forming oblique cases of the first person plural personal pronoun (source also of Sanskrit nas, Avestan na, Hittite nash "us;" Greek no "we two;" Latin nos "we, us;" Old Church Slavonic ny "us," nasu "our;" Old Irish ni, Welsh ni "we, us"). The -n- is preserved in Germanic in Dutch ons, German uns.
<a href="https://www.etymonline.com/word/nobis">Etymology of nobis by etymonline</a>
Harper, D. (n.d.). Etymology of nobis. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/nobis