Two senses to keep apart: blackmail/extortion as in 讹诈 and 敲诈-style 讹人 (to shake someone down), and 'textual error' as in 讹误 and 以讹传讹 (errors compounding as they spread).
Left-side speech radical 讠, the simplified form of 言. Both senses — false words/errors and verbal intimidation — are about speech, which the radical signals.
