bachelor-at-arms vs knight bachelor

bachelor-at-arms and knight bachelor both are nouns.

Word	Noun	Adjective	Verb	Adverb
bachelor-at-arms	Yes	No	No	No
knight bachelor	Yes	No	No	No

As nouns, bachelor-at-arms and knight bachelor are synonyms defined as:

bachelor-at-arms and knight bachelor: a knight of the lowest order; could display only a pennon

Other synonyms of bachelor-at-arms include bachelor.

bachelor-at-arms (noun)	knight bachelor (noun)
a knight of the lowest order; could display only a pennon	a knight of the lowest order; could display only a pennon