ABSTRACT:  This paper considers the factors that may incline a language speaker to use a loanword when an equivalent first language term is already available. The paper begins by drawing evidence from New Zealand English, where words of Maori origin are an increasing presence, to demonstrate that a diachronic shift from English language to Maori language synonyms is occurring. This shift has contributed to ongoing nativization of New Zealand English through an increase in the use of both Maori word types and tokens. The reasons for this shift are then considered, and six factors that may account for changes in an individual speaker's lexical choices are proposed.