Ernest Weekley, The Romance of Words (4th ed.)
“ The ferrule of a walking-stick is a distinct word from ferule, an aid to education. The latter is Lat. ferula, "an herbe like big fenell, and maye be called fenell giant. Also a rodde, sticke, or paulmer, wherewith children are striken and corrected in schooles; a cane, a reede, a walking staffe" (Cooper) . Ferrule is a perversion of earlier virrel, virrol, Fr. virole, "an iron ring put about the end of a staffe, etc., to strengthen it, and keep it from riving" (Cotgrave) .The modern meaning of pester is due to a wrong association with pest. ”
