平家が専横を極める中、それまで正四位下を極位としていた清和源氏としては突出した従三位に叙せられたことから源三位（げんざんみ）と称された。
Amid the political domination by the Taira family, he was granted Jusanmi (Junior Third Rank), the highest ever granted to anybody in the Seiwa-Genji (Minamoto clan), with the highest rank before him being Shoshiinoge (Senior Fourth Rank, Lower Grade); thus, he was called Gen-zanmi. - Wikipedia日英京都関連文書対訳コーパス
このため、平家一門が三位以上に列せられたのに続いて、当時、源氏の傍流となっていた摂津源氏の源頼政が、源氏として初めて従三位に昇った際には、異例とされ、世に源三位（げんざんみ）と称された。
Thus, when MINAMOTO no Yorimasa of Settsu-Genji (Minamoto clan), who had become a tributary of the Minamoto clan at that time, became the first from the Minamoto clan to be promoted to Jusanmi, after the Taira family were granted Sanmi and higher ranks, it was considered exceptional and was referred to as Genzanmi. - Wikipedia日英京都関連文書対訳コーパス
