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.
Words nearby get to the bottom of
get through one's head,
get through to,
get to,
get to first base,
get to one's feet,
get to the bottom of,
get to the heart of,
get to the point,
get together,
get tough with,
get under one's skin