[1] : The Collaborative International Dictionary of English v.0.48

quidam \qui"dam\, n. l.
   somebody; one unknown. --spenser.
   1913 webster

[2] : Bouvier's Law Dictionary, Revised 6th Ed (1856)

quidam, french law. some, one; somebody. this latin word is used to express 
an unknown person, or one who cannot be named. 
     2. a quidam is usually described by the features of his face, the color 
of his hair, his height, his clothing, and the like in any process which may 
be issued against him. merl. repert. h.t.; encyclopedie, h.t. 
     3. a warrant directing the officer to arrest the "associates" of 
persons named, without naming them, is void. 3 munf. 458. 

Quidam >> Q Words
Quidam, definition of term: Quidam
quidam_pag1.html