Jonkvrouw

Jonkheer (female equivalent: Jonkvrouw) is a Dutch honorific of nobility. In Belgium, the title of Écuyer (in French) or Jonkheer/Jonkvrouw (in Dutch) is the lowest title within the nobility system, recognised by the Court of Cassation. It is the cognate and equivalent of the German noble honorific Junker, which was historically used throughout the German-speaking part of Europe, and to some extent also within Scandinavia.

Jonkheer or Jonkvrouw is literally translated as "young lord" or "young lady". In medieval times such a person was a young and unmarried son or daughter of a high-ranking knight or nobleman. Many noble families could not support all their sons to become a knight because of the expensive equipment so the eldest son of a knight was a young lord while his brothers remained as esquires.

However, in the Low Countries (and other parts of continental Europe), only the head of most noble families carries a title, inheritance being by male lineage. That resulted therefore that most of the nobility is untitled in the Netherlands. 'Jonkheer', or its female equivalent 'jonkvrouw' developed therefore quite early into a different but general meaning: an honorific to show that someone does belong to the nobility/but does not possess a title. The abbreviation jhr., or jkvr. for women, is placed in front of the name (preceding academic, but not state titles).

The honorific could be compared more or less with "Edler" in Austria or "Junker" in Germany, though due to circumstances of German and especially Prussian history, "Junker" assumed connotations of militarism absent from the Dutch equivalent. Comparing it with the English nobility, it could be roughly translated as "The Honourable", when the untitled person is a son or daughter of a hereditary knight, baron, viscount or count, or "Lord" or "Lady", when the untitled person is member of the old (Dutch) nobility, untitled but of high ranking, and from preceding 1815 (i.e. "Heer van X" or Lord of X).

...
Wikipedia