We enjoyed this bit of trivia today in James Kilpatrick's column:
The Court of Peeves, Crochets & Irks resumes its autumn assizes with a petition from Jeanne Schapper from Somewhere in Cyberspace. She asks for definitive guidance on "farther" and "further."
Every commentator on English usage has had a go at this one. Their advice boils down to an agreeable consensus: Use "farther" for concepts of distance, both literal and figurative. Use "further" for concepts of degree. Thus, Stern Father says to Willful Daughter, "Do not push my patience any farther!" She replies, "I will not impose upon your patience any further."
The court's rule is a "mostly" rule -- i.e., it works most of the time, but we're sailing here on a most uncertain sea.
The original word, many centuries ago, appears to have been "further." After a few years, some scribe misspelled it as "farther." It was a typographical error. People took sides. To this day the distinctions are better understood than explained. Let us move on.