Where does “右大臣” come from?

右大臣 (Japanese) comes from Japanese 右, from Middle Chinese 右.

右大臣 (Japanese): the minister of the right, a government position in the 太政官||Great Council of State|pos=the highest government office under the 律令}} system}}

Definitions

the minister of the right, a government position in the 太政官||Great Council of State|pos=the highest government office under the 律令}} system}}

Ancestry of “右大臣”, step by step

右大臣 traces back through 3 separate lines of ancestry.

via Japanese 右

Step	Language	Word	Meaning
1	Japanese	右	right; the above statement, foregoing; the right...
2	Middle Chinese	右	—

via Japanese 大臣

Step	Language	Word	Meaning
1	Japanese	大臣	a government minister of Japan or ancient China

via Japanese 大殿

Step	Language	Word	Meaning
1	Japanese	大殿	—

Every word from Middle Chinese 右 →Every word from Japanese 右 →