This dissertation concerns personal nicknames in Modern and Old Icelandic. Responses to a written survey on contemporary nickname use include a variety of narrative explanations. Child pronunciation and endearments are frequently mentioned as sources of nicknames used in the family circle. Other types of nicknames are associated with school peer groups, fishing boats and rural communities. Informants' impressions of geographical variation or diachronic trends relate to local identity and general societal changes.

The 1400 examples found in the survey responses form the basis for a discussion of the phonology of Modern Icelandic nicknames. Most properties typical of nicknames can be viewed as reductions in markedness, many of which are also seen in child language. The highly irregular correspondence between nicknames and names is less morphological derivation than shared reference and connotation. However, it is possible to identify some comparatively regular subpatterns. A nickname may maintain the segmental content of the base within the prosodic template. Other nicknames show avoidance of dental continuants. Medial geminates are found in over half the examples; gemination most often entails avoidance of dental continuants.

Definitional and philological questions arise in determining which names found in medieval texts constitute suitable data for comparison with modern nicknames. Hypocoristics are seldom attested in alternation with other forms of personal names. Differences among lists of Old Norse nicknames compiled by other scholars reflect different assumptions made in the face of limited data. A composite of these lists is compared with a list compiled in the mid-eighteenth century and with twentieth-century data. Apparent changes relate to developments in the structure of Icelandic. A shift from a þ:t to a þ:d alternation in the correspondence between names and nicknames provides evidence for an Icelandic consonant shift, i.e., that the contrast between t and d was one of voicing rather than aspiration in Old Icelandic. A new [l:] has emerged in nicknames by analogy with other geminates in nicknames.

There is chronological and cultural variation in definitions of official vs. unofficial personal names. True and false names, naming and renaming are recurrent motifs in Old Norse literature.