RichThesaurus
get something off one's chest
vs
vent one's spleen
get something off one's chest
vent one's spleen
verb
To openly express pent-up anger, often on an unrelated matter or person.
How often have the words
get something off one's chest
and
vent one's spleen
occurred in a corpus of books?
(source:
Google Ngram Viewer
)