It is the abnormal enthusiasm for flogging.
The Latin word for whip is flagellum. English derives several words from there:Some unicellular organisms get around by swinging their flagella, or whip-like appendages.Self-flagellation, a form of corporal punishment involving -- that's right -- whips was common during the Black Death among those who believed the Plague was a punishment from God.A flagellophile collects whips; he may suffer from flagellomania, an obsession with whipping or being whipped.Attila the Hun was known to the Romans as Flagellum Dei, or the Scourge (Whip) of God.