the curb put into the mouths of horses to restrain them

The Hebrew word metheg so rendered in Psalm 32:9 is elsewhere translated “bridle” (2 Kings 19:28; Proverbs 26:3; Isaiah 37:29).

Bits were generally made of bronze or iron, but sometimes also of gold or silver.

In James 3:3 the King James Version translates the Greek word by “bits,” but the Revised King James Version by “bridles.”