Dictionary.com/obdurate:

obdurate (OB-du-rit; OB-dyu-rit) adjective

1. 1. Hardened in wrongdoing or wickedness; stubbornly impenitent: “obdurate conscience of the old sinner” (Sir Walter Scott).
   2. Hardened against feeling; hardhearted: an obdurate miser.
2. Not giving in to persuasion; intractable. See Synonyms at inflexible.

[Middle English obdurat, from Late Latin obdrtus, past participle of obdrre, to harden, from Latin, to be hard, endure : ob-, intensive pref.; see ob- + drus, hard; see deru- in Indo-European Roots.]