Noun
nobiliary particle (plural nobiliary particles)
(grammar) A preposition found in names, indicating nobility.
He followed his father in the surname Balzac but added the aristocratic-sounding nobiliary particle to help him fit into respected society, a choice based on skill rather than by right. Source: Internet
Robb, 169 The timing of the decision was also significant; as Robb explained: "The disappearance of the father coincides with the adoption of the nobiliary particle. Source: Internet