bend over backwards vs fall over backwards

bend over backwards and fall over backwards both are verbs.

Word	Noun	Adjective	Verb	Adverb
bend over backwards	No	No	Yes	No
fall over backwards	No	No	Yes	No

As verbs, bend over backwards and fall over backwards are synonyms defined as:

bend over backwards and fall over backwards: try very hard to please someone

bend over backwards (verb)	fall over backwards (verb)
try very hard to please someone	try very hard to please someone