Thane (Title)

"Then by my right as Jarl, I name you Thane of Hold. Congratulations. I grant you this weapon from the armory to serve as your Badge of Office. I'll also notify the Guards of your new title, wouldn't want them to think you're part of the common rabble now."

- Jarl Balgruuf The Greater

The Thane is someone recognized by a Jarl, his guards, and the people, as a person of great importance in a particular city, often a hero. They have contributed to a Hold significant deeds that have helped the Jarl of the Hold and its people with problems and tasks. Newly titled Thanes receive housecarls, sworn bodyguards who protect the Thane, their spouses, and their property.

The Elder Scrolls V: Skyrim
The title of Thane is an honor gifted by a city's Jarl to the Dragonborn. It is only granted if the Dragonborn completes tasks for people of the hold, and personally assists the Jarl in official or unofficial business, depending on the city. Rarely, if the Dragonborn has enough Septims, the title of Thane may be given.

The guards of the Hold excuse the Dragonborn from crimes if they mention they are the Thane in a dialogue option when confronted, but this only works once. After being proclaimed Thane in a city, the Dragonborn can purchase houses from the Jarls' stewards. In a few rare cases, purchasing a home within a Hold is a prerequisite for becoming a Thane of said Hold, such as the Rift.

The Elder Scrolls Online
During the Second Era, Thanes are prevalent throughout Skyrim, each having contributed deeds and acts of heroism for their Holds. The Vestige meets and helps out most of the thanes with dealing with the Stormfist Brigade as part of the royal retinue of King Jorunn going around Eastmarch. Though it isn't specified to which holds most of the thanes belong to, they are all part of the royal council of the King as he meets with the other leaders of the Ebonheart Pact in Skyrim.

The Elder Scrolls V: Skyrim

 * Erikur serves as Thane to Elisif, Jarl of Solitude. Melaran, an Altmer alterer, serves as Erikur's housecarl, If Erikur dies, Melaran will replace him as thane.
 * Bryling serves as Thane to Elisif, Jarl of Solitude. Irnskar Ironhand serves as Bryling's housecarl. If Bryling dies, Irnskar will replace her as thane.
 * Dengeir of Stuhn, Former Jarl of Falkreath Hold now serves his nephew, Jarl Siddgeir, as Thane.

The Elder Scrolls Online

 * Mera Stormcloak serves Windhelm, member of the ancient Stormcloak Clan of Windhelm and oversees the city's protection.
 * Harvald is one of King Jorunn's closest advisors and a veteran at war.
 * Oda Wolf-Sister accompanies the High King throughout the Pact's council. Jaema is Oda's housecarl, often having a hard time trying to find her thane as Oda prefers the company of wolves.
 * Jeggi Gap-Tooth is bear of a man and has impressed Pact delegates for his immense drinking skill and is often seen drunk. He accompanies the Pact council throughout Eastmarch.

Real-world meaning
The Thanes (Thegns) were the minor nobility of Anglo-Saxon England and Viking Scandinavia -- the word literally means a retainer to a king or high-ranking official. This, however, has been observed to have been an honorary task and title in many early medieval Scandinavian cultures.

Many runestones in Sweden and Denmark honor dead men as good thanes.

Appearances

 * The Elder Scrolls V: Skyrim
 * The Elder Scrolls Online