Junker is derived from Middle High German Juncherre, meaning "young nobleman" or otherwise "young lord" (derivation of jung and Herr), and originally was the title of members of the higher edelfrie (immediate) nobility without or before the accolade. It evolved to a general denotation of a young or lesser noble, often poor and politically insignificant, understood as "country squire" (cf. Martin Luther's disguise as "Junker Jörg" at theWartburg; he would later mock King Henry VIII of England as "Juncker Heintz." As part of the nobility, many Junker families only had prepositions such as von or zu before their family names without further ranks. The abbreviation of the title is Jkr., most often placed before the given name and titles, for example: Jkr. Heinrich von Hohenberg. The female equivalent Junkfrau (Jkfr.) was used only sporadically. In some cases, the honorific Jkr. was also used for Frieherren (Barons) and Grafen (Counts).

A good number of poorer Junkers took up careers as soldiers (Fahnenjunker), mercenaries, and officials (Hofjunker, Kammerjunker) at the court of territorial princes. These families were mostly part of the German medieval Uradel and had carried on the colonization and Christianization of the northeastern European territories during the Ostsiedlung. Over the centuries, they had become influential commanders and landowners, especially in the lands east of the Elbe River in the Kingdom of Prussia. As landed aristocrats, the Junkers owned most of the arable land in Prussia. Being the bulwark of the ruling House of Hohenzollern, the Junkers controlled the Prussian Army, leading in political influence and social status, and owning immense estates, especially in the north-eastern half of Germany (i.e. the Prussian provinces of Brandenburg, Pomerania, Silesia, West Prussia, East Prussia and Posen). This was in contrast to the predominantly Catholic southern states such as the kingdoms of Bavaria or the Grand Duchy of Baden, where land was owned by small farms, or the mixed agriculture of the western states like the Grand Duchy of Hesse or even the Prussian Rhine and Westphalian provinces.