Webster's 1828 Dictionary
CREDENTIALS
n.plu. [Rarely or never used in the singular. ] That which gives credit; that which gives a title or claim to confidence; the warrant on which belief, credit or authority is claimed, among strangers; as the letters of commendation and power given by a government to an embassador or envoy, which give him credit at a foreign court. So the power of working miracles given to the apostles may be considered as their credentials, authorizing them to propagate the gospel, and entitling them to credit.
American Oxford Thesaurus
credentials
credentials plural noun checking the driver's credentials: documents, documentation, papers, identity papers, bona fides, ID, ID card, identity card, passport, proof of identity; certificates, diplomas, certification, references.
Oxford Thesaurus
credentials
credentials plural noun the policemen went to check the driver's credentials: documents, papers, identity papers, identification papers, bona fides; warrant, licence, permit, pass, ID, card, ID card, identity card, passport, proof of identity, proof of qualifications, certificate, diploma, voucher, documentation; references, testimonial, letter of introduction, letter of recommendation, missive, deed, title.