The Collaborative International Dictionary of English v.0.48:
Onomasticon \On`o*mas"ti*con\, n. [NL., fr. Gr. ? (sc.?), fr. ?. See Onomastic.] A collection of names and terms; a dictionary; specif., a collection of Greek names, with explanatory notes, made by Julius Pollux about a. d. 180. [1913 Webster]WordNet (r) 3.0 (2006):
onomasticon n 1: a list of proper nouns naming persons or places