sabre rattling vs saber rattling

sabre rattling and saber rattling both are nouns.

Word	Noun	Adjective	Verb	Adverb
sabre rattling	Yes	No	No	No
saber rattling	Yes	No	No	No

As nouns, sabre rattling and saber rattling are synonyms defined as:

sabre rattling and saber rattling: the ostentatious display of military power (with the implied threat that it might be used)

sabre rattling (noun)	saber rattling (noun)
the ostentatious display of military power (with the implied threat that it might be used)	the ostentatious display of military power (with the implied threat that it might be used)