The word baron comes from the Old French baron, from a Late Latin baro "man; servant, soldier, mercenary" (so used in Salic Law; Alemannic Law has barus in the same sense). The scholar Isidore of Seville in the 7th century thought the word was from Greek βαρύς "heavy" (because of the "heavy work" done by mercenaries), but the word is presumably of Old Frankish origin, cognate with Old English beorn meaning "warrior, nobleman". Cornutus in the first century already reports a word barones which he took to be of Gaulish origin. He glosses it as meaning servos militum and explains it as meaning "stupid", by reference to classical Latin bārō "simpleton, dunce"; because of this early reference, the word has also been suggested to derive from an otherwise unknown Celtic *bar, but the Oxford English Dictionary takes this to be "a figment".
During the Ancien Régime, French baronies were very much like Scottish ones. Feudal landholders were entitled to style themselves baron if they were nobles; a roturier (commoner) could only be a seigneur de la baronnie (lord of the barony). These baronies could be sold freely until 1789 when feudal law was abolished. The title of baron was assumed as a titre de courtoisie by many nobles, whether members of the Nobles of the Robe or cadets of Nobles of the Sword who held no title in their own right. Emperor Napoléon created a new empire nobility, in which baron was the second lowest title. The titles followed a male-only line of descent and could not be purchased. In 1815, King Louis XVIII created a new peerage system based on the British model. Baron-peer was the lowest title, but the heirs to pre-1789 barons could remain barons, as could the elder sons of viscount-peers and younger sons of count-peers. This peerage system was abolished in 1848.
In pre-republican Germany all the knightly families of the Holy Roman Empire (sometimes distinguished by the prefix von or zu) eventually were recognised as of baronial rank, although Ritter is the literal translation for "knight", and persons who held that title enjoyed a distinct, but lower, rank in Germany's nobility than barons (Freiherren). The wife of a Freiherr (Baron) is called a Freifrau or sometimes Baronin, his daughter Freiin or sometimes Baroness.
Families which had always held this status were called Uradel ('primordial/ancient/original nobility'), and were heraldically entitled to a three pointed coronet. Families which had been ennobled at a definite point in time (Briefadel or "nobility by patent") had seven points on their coronet. These families held their fief in vassalage from a suzerain. The holder of an allodial (i.e., suzerain-free) barony was thus called a Free Lord, or Freiherr. Subsequently, sovereigns in Germany conferred the title of Freiherr as a rank in the nobility, without implication of allodial or feudal status.
Today, as of 1919 on, there is no legal privilege associated with hereditary titles in Germany. In modern, republican Germany, Freiherr and Baron remain heritable only as part of the legal surname (and may thereby be transmitted by males to their wives and children, without implication of nobility). As opposed to this, hereditary titles have been banned completely in Austria. Thus, a member of the formerly imperial House of Habsburg or any other member of the former nobility would in most cases simply be addressed as "Herr/Frau (Habsburg)" in an official/public surrounding, for instance in the media. Still, in both countries, honorary styles like "His/her (Imperial/Royal) Highness", "Serenity", etc. persists in social use as a form of courtesy.