E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Neck-verse (Psalm li. 1).
Have mercy upon me, O God, according to Thy lovingkindness: according unto the multitude of Thy tender mercies blot out my transgressions. This verse was so called because it was the trial-verse of those who claimed benefit of clergy;
and if they could read it, the ordinary of Newgate said, Legit ut clercus, and the convict saved his neck, being only burnt in the hand and set at liberty.