credential

A credential is a qualification that proves you are entitled to do something. A certificate, a licence, a card.

It is nearly always plural, and checking somebody's credentials means confirming they are what they claim to be. The word covers formal qualifications and, more loosely, evidence of suitability, so green credentials or democratic credentials mean a record that proves the claim. Computing uses it precisely for a username and password. The verb to credential is chiefly American, and accreditation is the process of granting them.