What is "nobiliary particle"

n. (context grammar English) a preposition found in names, indicating nobility

A nobiliary particle is used in a surname or family name in many Western cultures to signal the nobility of a family. The particle used varies depending on the country, language and period of time. However, in some languages the nobiliary particle is the same as a regular prepositional particle that was used in the creation of many surnames. In some countries it became customary to distinguish the nobiliary particle from the regular one by different spelling, although in other countries these conventions did not arise, occasionally resulting in ambiguity.