These words came truly from the bottom of his heart.
Tips
usage
In traditional medicine the body's organs split into 脏 (solid viscera) and 腑 (hollow organs like stomach and intestines). The phrase 肺腑之言 means words from the depths of one's heart.
Right 府 supplies the sound — fǔ with no tone shift. Its sense of an inner storehouse loosely echoes the body's internal organs, but its main job is phonetic. The same phonetic appears in 腐.