Sif-ilis

An infectious disease caused by a mischief, usually transmitted by random acts of stupidity, marked initially by irritation and progressing to groin pain. Outbreaks recur cyclically. If left untreated long enough, can lead to madness.

Origin: Loki television series, Season 1, Episode 4, "The Nexus Event"
Etymology: Old Norse

Loki contracted Sif-ilis following an ill-advised attempt to cut Sif's hair.