Accidavy, an inveterate corruption of affidavit. Sometimes simply davy.
We think nowse on’t, aw’ll myek accydavy. – Canny Newcassel.
Source: Brockett John Trotter. A Glossary of North Country Words in use with Etymology and affinity to other languages and occasional Notices of Local Customs and Popular Superstitions. Printed Newcastle upon Tyne 1829.