fall down

/F AO1 L D AW1 N/
verb
  1. 1

    To fall to the ground. To collapse.

    โ€œRing a-ring o' roses, / A pocketful of posies. / A-tishoo! A-tishoo! / We all fall down. โ€” traditional nursery rhyme (British version)โ€

  2. 2

    To sail or drift toward the mouth of a river or other outlet.

  3. 3

    To fail.

    โ€œThat is where your reasoning falls down.โ€

Source: https://en.wiktionary.org/wiki/fall%20down