https://en.wikipedia.org/wiki/Demon_core

The demon core was a sphere of plutonium–gallium alloy that was involved in two fatal radiation accidents when scientists tested it as a fissile core of an early atomic bomb.

Scientists referred to this flirtation with a nuclear chain reaction as “tickling the dragon’s tail”, based on a remark by physicist Richard Feynman.[12][13]

It was a case of an unfortunate mistranslation due to the lack of awareness among historians about the thriving scalie scene at the Manhattan Project.