bottom of it, at the/get to the

get to the bottom of something

Fig. to get an understanding of the causes of something. We must get to the bottom of this problem immediately. There is clearly something wrong here, and I want to get to the bottom of it.
See also: bottom, get, of
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

get to the bottom of

Find the basic underlying quality or cause of something. For example, He was determined to get to the bottom of the problem. [Late 1700s] Also see at bottom.
See also: bottom, get, of
The American Heritage® Dictionary of Idioms by Christine Ammer.

get to the bottom of

find an explanation for (a mystery).
See also: bottom, get, of
Farlex Partner Idioms Dictionary

bottom of it, at the/get to the

To discover the origin of a problem, or the fundamental truth of an issue or event. The word “bottom” has been used in this way (to mean ultimate cause) since the sixteenth century. Shakespeare used it numerous times, as in “Is there no pity . . . that sees into the bottom of my grief?” (Romeo and Juliet, 3.5). Several early proverbs also refer to “bottom” in this way: “If thou canst not see the bottom, wade not”; and “He brought the bottome of the bag cleane out” (John Heywood, 1546). The pioneer anthropologist James Burnett, Lord Monboddo, wrote in 1773 (Of the Origin and Progress of Language), “In order to get to the bottom of this question.”
See also: bottom, get, of
The Dictionary of Clichés by Christine Ammer
See also:
  • a/the feel of (something)
  • (I) wouldn't (do something) if I were you
  • a straw will show which way the wind blows
  • a crack at (someone or something)
  • all right
  • (you) wanna make something of it?
  • all for the best
  • a thing of the past
  • a slew of (something)
  • a bird in the hand