köken: Inherited from Middle High German übermorgen, from Old High German ubar morgan, ubar morgana; equivalent to über- (“over, above”) + morgen (“tomorrow”). Compare Dutch overmorgen, Yiddish איבערמאָרגן (ibermorgn).
Nietzsche Erst das Übermorgen gehört mir
Dem Abschied von allem Möglichen des Morgens und des Übermorgens
köken: From birisi + gün. Cognates Compare Karachay-Balkar бюрсюкюн (bürsükün) /бюрсикюн (bürsikün), Kumyk бирисигюн (birisigün), Kazakh бүрсігүні (bürsıgünı), Nogai бирсигуьн (birsigün), Kyrgyz бүрсүгүнү (bürsügünü), Southern Altai бирсӱӱн (birsüün), Karaim birisikün etc., some of which mean 'the day before yesterday' and some - 'the day after tomorrow'.
ngày (“day”) + kia. For the semantic relationship, compare Chinese 後日 /后日 (hòurì) and 後天 /后天 (hòutiān). Not to be confused with hôm kia (“day before yesterday”).