The Greek and Hebrew that is translated as “birthright” in most English translations is translated in Guhu-Samane as “the right of the first child of the vine.”
Source: Ernest Richert in The Bible Translator, 1965, p. 81ff.
Verse: Gen 25:31
וַיֹּ֖אמֶר יַעֲקֹ֑ב מִכְרָ֥ה כַיּ֛וֹם אֶת־בְּכֹֽרָתְךָ֖ לִֽי׃
Retrieving the verse