Delete Siri and Dictation history on Mac
Your requests are associated with a random identifier, and not with your Apple ID. You can delete request history that is associated with a random identifier and less than six months old (you must be connected to the internet).
On your Mac, choose Apple menu > System Preferences, then click Siri.
Click Delete Siri & Dictation History.
Important: Deleting Siri and Dictation history doesn’t change the choice you made about sharing audio recordings. To change that setting, see Change Privacy preferences.