Fairfax High School, a reliable enough source, says that “Fairfax” refers to Thomas, Baron Cameron, 6th Lord Fairfax (1693-1781), friend and neighbor of George Washington and the only British noble to live in the American colonies. (Fairfax High’s Greenway Court Theatre is named after Lord Fairfax’s Virginia estate.) I don’t know why the City of L.A. chose him as this avenue’s honoree, but my guess is that “Fairfax” was simply a common enough place name, it sounded nice, and it was available. The street was originally called Crescent Avenue back in 1887 – you may presume that’s how Crescent Heights got its name – and a June 6th, 1912 news brief noted that City Council was renaming it “West Street” when property owners protested. Four months later, apparently to little protest, it quietly became Fairfax Avenue. Bits of Crescent survived until 1921, when the whole thing officially became Fairfax.