Why is "Friends" capitalized in 1 Maccabees in the NRSV?

Throughout 1 Maccabees in the NRSV, "Friends" is capitalized when referring to the King's friends. Why is this? My only guess is it's an official title. Specifically, I would like to ask about 1 Maccabees 2:18: > Now be the first to come and do what the king commands, as all the > Gentiles and the people of Judah and those that are left in Jerusalem > have done. Then you and your sons will be numbered among the Friends > of the king, and you and your sons will be honored with silver and > gold and many gifts.” [NRSV]