236 Get the bottom of

(PW) find out the real cause

After talking to my friend for an hour, I finally got to the bottom of why he was angry at me.

 

(your)

Find the basic underlying quality or cause of something. For example, He was determined to get to the bottom of the problem. [Late 1700s]

 

(englishclub) If you get to the bottom of something, you find out its real cause or the true story behind it.

• The police don't know who did the robbery yet, but they promised to get to the bottom of it.
• I'm not sure how a mistake like this could happen, but I'm determined to get to the bottom of it and make sure it never happens again.

(GoEnglish)

Get To The Bottom Of This (find out the truth about what has happened ... )

 

(1-language) - GET TO THE BOTTOM OF -

Reaching a state of conclusion over an issue or subject. For example:

In a murder investigation, the lead detective could tell a peer that they will "get to the bottom of this case," meaning they will solve the case.