deceitful. crooked. Referring to the old nature of the natural man. desperately wicked. sick unto death. it [is] sick unto death: i.e. it [is] incurable.
who can know it? Figure of speech Erotesis, for emphasis.
Related Commentaries of Jeremiah 17:9
Jeremiah 17:9
9 The heart is deceitful above all things, and desperately wicked: who can know it?