The story
A reference to the Holy Hand Grenade of Antioch, a fictional weapon featured in the 1975 film Monty Python and the Holy Grail. The weapon is a satirical interpretation of a globus cruciger (specifically, the Sovereign's Orb), hence Sense 2. The popularity of holy hand grenades as video game items is largely attributed to the Worms series.
Etymology from Wiktionary, CC BY-SA 4.0.