Late 16th century. From classical Latin quīdam a certain (unspecified) person from quis (indefinite pronoun) somebody, anybody + -dam, of uncertain origin.
Definition of quidam in US English:
quidam
nounˈkwiːdam
An unknown or unspecified individual; somebody.
Origin
Late 16th century. From classical Latin quīdam a certain (unspecified) person from quis (indefinite pronoun) somebody, anybody + -dam, of uncertain origin.