One of the most import aspects of Clash of Clans are clans themselves. But what is a clan and how historically accurate are clans in the game?
Clans
The word
clan is derived from the Gaelic word
clanna, meaning
children. A clan is a kinship group among people. The clans in Clash of Clans are based on Scottish or Finnish type clans (Supercell itself is based in Finland). We can see many similarities between the game clans and real life.
Clan Leaders
Players of Clash of Clans are referred to by the game as "Chief". However, in Scottish clans the clan chief is the leader of the clan.
The clan co-leaders are somewhat akin to the Scottish clans' nobility or
fine as they have more power than normal clan members.
Clan Identity
In Clash of Clans, clans can be easily identified by their names and symbols. Most Scottish clans have names that are now recognizable first or last names common today. For example, Keith, Leslie, Scott, Mackenzie, Campbell, Gordon, or even Clan Ranald Macdonald (now a very popular fast food mascot).
Clan crest badges are not historically accurate, being romanticized in the Victorian era, but are somewhat close to the symbols that represent in-game clans. These crest badges do not actually represent a clan, but the leader of the clan.

A better analogy would be clan badges, also known as plant badges. These consist of a piece of a plant, particular to each clan, for example, a holly leaf.
According to Scottish lore, badges were used to identify members of the clan during battles. Clan badges are commonly referred to as the original clan symbol, however some scholars claim that the clan chiefs' heraldic flags are the earliest way of clan identification.
Battles
Scottish clans frequently fought among each other and clan members were forced to pay rents known as
calps to fund these wars somewhat like troop donating in clash of clans.