The story
- Danish · derived fromkoagulation
- English todayvitamin K
Named similarly to the other vitamins, that are named after their order of discovery. This one was assigned its "K" from Danish koagulation by the Danish researcher Henrik Dam. The sense that is a slang alias for ketamine is because of the initial letter of that drug's name, as also with the slang sense of Special K.
Etymology from Wiktionary, CC BY-SA 4.0.