This article examines the structure and usage of nicknames given to professional hockey and baseball players. Two general types are observed: a phrasal referring expression and a single-word hypocoristic. The phrasal nickname is descriptive but is only used referentially, usually in sports narrative. The hypocoristic is used for both reference and address and may be descriptive or shortened from a formal name. In addition, its inclusion of a hypocoristic suffix is sensitive to the segmental content of the shortened form. A model of nickname assignment is proposed in which the creation of any kind of nickname is treated as enriching the lexicon. This model relates nicknames to other types of specialized or elaborate referring expressions and encodes the social meaning of nicknames and other informal names in the lexicon.