Amarna Canaanite

up-sí-ḫi - extremity (DNWSI 97)

In EA 366:34, as a gloss to ZAG!.ḪI<.A>-ši (Rainey 1978:34‒35, 98). For a different evaluation v. van Soldt 1997, who prefers to relate up-sí- to Ugr. ˁbs/ˁps ‘landmark, boundary’ (DUL 174)

*ˀaps- - extremity (HALOT 79, DRS 29, Kogan 2015: 283)

as suggested by HALOT 79 and DRS 29, may be borrowed from Akk. apsû ‘cosmic subterranean water’, in its turn going back to Sum. abzu.