穷根究底

窮根究底
qiónggēnjiūdǐ
  1. to get to the bottom of the matter
  2. to make a thorough inquiry into something

Wiktionary

Entry Composition

1 穷 qióng
  1. poor
  2. destitute
  3. to use up
  4. to exhaust
  5. thoroughly
  6. extremely
  7. (coll.) persistently and pointlessly
2 根究 gēnjiū
  1. to investigate (sth) thoroughly
  2. to get to the bottom of
=3 底 de (equivalent to 的 as possessive particle)
=3 底 dǐ
  1. bottom; base
  2. background; foundation
  3. copy (of a manuscript or receipt etc) kept as a record
  4. (suffix) end of a year or month
  5. (math.) radix; base (abbr. for 底数 dǐshù)