nobiliary particle
Definition - A preposition that forms a part of an aristocratic title.

Example -
The French use de (e.g. Joseph de Maistre) and the Germans use von (e.g. Baron Manfred von Richthofen). In both cases the preposition means "of."

Oxford English Dictionary -
The term's first citation is from 1871:
"The law, which forbids persons to adopt nobiliary particles to which they have no right."
(Member for Paris II. 15)

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