Russia on Monday threatened to strike British military facilities and said it would hold drills simulating the use of battlefield nuclear weapons amid sharply rising tensions over comments by senior Western officials about possibly deeper involvement in the war in Ukraine.
After summoning the British ambassador to the Foreign Ministry, Moscow warned that Ukrainian strikes on Russian territory with U.K.-supplied weapons could bring retaliatory strikes against British military facilities and equipment on Ukrainian soil or elsewhere.
The remarks came on the eve of Russian President Vladimir Putin’s inauguration to a fifth term in office and in a week when Moscow on Thursday will celebrate Victory Day, its most important secular holiday, marking its defeat of Nazi Germany in World War II.
Hmm. I wonder where it came from. Might have been German.
goes to check etymonline
Gives the date of first-known use, but not where. I assume that that means that this was in English, since normally they list the origin language.
https://www.etymonline.com/search?q=saber+rattling
EDIT: Oooh, etymonline is wrong (or at least not complete). Mirriam-Webster has earlier known uses, says that it was used in the UK first, around the late 1870s.
https://www.merriam-webster.com/wordplay/saber-rattling-word-history
I wondered who was first, too, and looked it up before. The date seems to be in dispute, but English is apparently the original language to coin the term.