A region in eastern Beleriand translated Ossiriand glossed “Land of Seven Rivers” (S/94), a reduction of primitive otoso “seven” combined with sîr “river” and the suffix -ian(d) “-land” (RC/384).
Conceptual Development: In the earliest Silmarillion drafts from the 1930s, this name first appeared as Assariad (SM/133) and on early maps as Ossiriath “of the Seven Rivers” (SM/233), but was soon revised to N. Ossiriand “Land of Seven Streams” (SM/116), the form it retained thereafter. Later in the 1930s its gloss was changed to “Land of Seven Rivers” (LR/128).
A shorter form of the name Ossiriand glossed “Seven-rivers” (LotR/469), a reduction of primitive otoso “seven” combined with sîr “river” (RC/384).