In Chini, a language of northeastern New Guinea, speakers rely on principles of semantic extension including metonymy, metaphor, and other types of association to create new terms using material from the vernacular. They do so in a special sociolinguistically marked register referred to here as ‘secret language’, a linguistic practice not unheard of in New Guinea. The same principles at work in secret language can also be seen in the creation of terms for new, modern concepts in the sociolinguistically unmarked register of the language. There is additionally some degree of overlap between the two registers, since what were originally secret language terms have entered into use in the unmarked register. This suggests that secret language has been a resource for resistance to borrowing and brings into focus the larger point that any understanding of borrowability should be rooted in the local sociolinguistic context, to the locally relevant ideologies at work and the particular creative principles of language use that speakers employ.