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—both audio recordings and transcripts—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 Settings, then click Siri & Spotlight in the sidebar. (You may need to scroll down.)
On the right, 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 & Security settings.