1
general::
Also, fall upon. 1. Attack suddenly and viciously, as in They fell on the guards and overpowered them. [c. 1400] 2. Meet with, encounter, as in They fell on hard times. [Late 1500s] 3. Find by chance, discover, as in We fell upon the idea last Saturday night. [Mid-1600s] 4. Be the responsibility or duty of someone, as in It fell on Clara to support the entire family. [Mid-1800s] Also see the subsequent idioms beginning with FALL ON.
American Heritage Idioms
2
general::
Phrase(s): fall on(to) someone or something
to collapse toward or onto someone or something. • The fence fell onto the car, denting it severely. • The branch fell on David., Phrase(s): fall (up)on someone
[for a task] to become the duty of someone. • The task of telling Mother about the broken vase fell upon Jane. • The job of cleaning up the spill fell upon Tom., Phrase(s): fall (up)on someone or something
1. to collapse on top of someone or something. (Upon is formal and less commonly used than on.) • The bridge fell upon a boat passing beneath it. • A small branch fell on Jerry as he passed beneath the tree. 2. to attack someone or something. • The cat fell upon the mouse and killed it. • The children fell on the birthday cake and ate it all.
McGrawhill's American Idioms And Phrasal Verbs