The sense found in Continental French, ‘homme de peine, portefaix’ seems hardly relevant here, even though etymologically both words are the same: the root of poena followed by the agential -or suffix. AND1’s original definition ‘executioner’ seems unlikely, as the word glosses multatores and appears listed among types of criminals who will be punished. Variant manuscripts gloss the same Latin word as murdrus (TLL ii 101.70) and tuourus (TLL ii 121.70). The attestation from TLL ii 163 lacks any further context, except that it glosses the Latin word tortor (‘one who inflicts severe pain, tormentor, torturer’, DMLBS 3459b).
It is unclear whether the word used in Court Bar is the same. In this case an association with punir is not impossible, but seems formally unlikely (when the stem should be punis- rather than pun- followed by an agent-suffix).