xenism
A word used in utterances of a language but generally marked as foreign.
The first stage is when a word from one language is used in an utterance of another language in order to create a somewhat exotic effect. At this stage, the word is not a borrowing, but rather what they term a xenism. An example of a xenism used in an English sentence would be At the harbour, we went for a sail in a gulet, where gulet is the word for a type of Turkish sail boat, which has no real equivalent in English.
Where it comes from
Borrowed from French xénisme, from Ancient Greek ξενισμός (xenismós, “strangeness, novelty”).
Adapted from the Wiktionary entry xenism (CC BY-SA 4.0).