This article presents an in-depth study of the Frisian loan pindakaas from Dutch pindakaas. This word can be literally glossed as ‘peanut cheese’, but it translates into English as ‘peanut butter’. The translation illustrates that the compound pindakaas is not compositional in Dutch and Frisian, that is, pindakaas is not a kind of kaas (‘cheese’). Because of its non-compositional nature, Dutch pindakaas, we argue, has not been borrowed into Frisian as pindatsiis, even though Dutch kaas in Frisian is tsiis. In contrast, compositional compounds featuring Dutch –kaas surface in Frisian with –tsiis, such as Dutch schapenkaas, Frisian skieppetsiis. The non-compositional nature of pindakaas is shown to have a historical explanation. Independent evidence is cited from psycholinguistics supporting the claim that compositional compounds behave in a way that differs from non-compositional ones. Thus evidence is provided that borrowing is sensitive to compositionality in that elements of compounds are more easily left untranslated when their meaning is not predictable by compositionality from their usage elsewhere in the language.