Earl was the Anglo-Saxon form and jarl the Scandinavian form of a title meaning "chieftain" and referring especially to chieftains set to rule a territory in a king's stead. In Scandinavia, it became obsolete in the Middle Ages and was replaced with duke (hertig/hertug); in later medieval Britain, it became the equivalent of the continental count (in England in the earlier period, it was more akin to duke, while in Scotland it assimilated the concept of mormaer).

In modern Britain, an earl is a member of the peerage, ranking below a marquess and above a viscount. The English never developed a feminine form of earl; the wife of an earl is styled countess (the continental equivalent).

Etymology

According to Procopius, the Heruli, after having raided the European continent for several generations, returned to Scandinavia in 512 AD as a result of military defeats. As their old territory was now occupied by the Danes, they settled next to the Geats in present-day Sweden. While the Proto-Norse word for this mysterious tribe may have been erilaz, which is etymologically near "jarl" and "earl", and it has often been suggested they introduced the runes in Scandinavia, no elaborate theory exists to explain how the word came to be used as a title. Arguably, their knowledge in interpreting runes also meant they were gifted in martial arts and, as they gradually integrated, eril or jarl instead came to signify the rank of a leader.Lindström, p 113-115

The Norman-derived equivalent "count" was not introduced following the Norman Conquest of England though "countess" was and is used for the female title. As Geoffrey Hughes writes, "It is a likely speculation that the Norman French title 'Count' was abandoned in England in favour of the Germanic 'Earl' 1 precisely because of the uncomfortable phonetic proximity to cunt".

The Irish, Scottish Gaelic, and Welsh words for "count" or "earl" (iarla in Irish and Scottish Gaelic, iarll in Welsh) are all descended from English "earl" or one of its ancestors. In Scotland the word earl was used in English to refer to a mormaer.

Forms of address

An earl has the title Earl of 2 when the title originates from a placename, or Earl 3 when the title comes from a surname. In either case, he is referred to as Lord 4, and his wife as Lady 5. A countess who holds an earldom in her own right also uses Lady 6, but her husband does not have a title (unless he has one in his own right).

The eldest son of an earl, though not himself a peer, is entitled to use a courtesy title, usually the highest of his father's lesser titles (if any); younger sons are styled The Honourable 7 8, and daughters The Lady 9 10 (Lady Diana Spencer being a well-known example).