Jolly Roger

The Jolly Roger (dokuro) is the traditional flag of European and American pirates, envisioned today as a skull over crossed thigh bones on a black field. Various versions of the Jolly Roger existed over the course of the centuries, for example Calico Jack's Jolly Roger replaced the thigh bones with swords (Cutlasses).

Oda himself provided some info on the Jolly Roger, including three possible theorized origins that have come to be accepted by experts:


 * Some say it comes from the French term "Jolie Rogue" or "red Lovely" possibly referring to blood.
 * "Roger" may have come from the word "Rogue" meaning thief or villain.
 * It may have come from the term "Old Roger" an old fashioned name for the Devil.

The Jolly Roger is hugely recognized to mean "danger" worldwide. The skull and crossbones themselves are commonly used on to warn people about dangerous substances or places on signs and bottles.

One Piece
In One Piece, there are many Jolly Roger flags. Jolly Rogers generally help pirates determine who belongs to whose crew, or even who is a pirate in the first place. Many choose to bare their crews flag somewhere on their personal being (such as Portgas D. Ace).

However, raising the Jolly Roger is considered a huge crime by the Marines, and anyone seen doing so (may it be fun or for real) will be considered criminals. The designs of the Jolly Roger usually reflect the interest or Captain of the crew. Other times it may be a personnel item they wear or the symbols behind them.

Ideals of the Flag
All those that sail under a Jolly Roger are suppose to show it respect for their chosen flag and honour it always as it represents the crew itself. Once the flag is gone, the crew can no longer sail under it and therefore everything linked with the flag is gone. Luffy uses this in making his choice in the Davy Back Fight and takes the Jolly Roger belonging to Foxy instead of a member of the crew, thus preventing ever flying under it again. He then gives them a new one he drew (badly) himself.

Different crews react differently to these ideals. For example, Wapol did not see what was so important about the pirate flag in comparison to Luffy. Donquixote Doflamingo does not like the idea of anyone tarnishing his flags name and punished Bellamy for losing under it.

Smilies
Following the introduction of Donquixote Doflamingo, a different type of Jolly Roger has appeared. Rather then the tradional skull and crossbones, the flag is a smilie, of a grinning person. The significance of this type of Jolly Roger has yet to be revealed. Yet in some cases, such as Domflamingo's flag and the Human Auction House the smilies has a "against" sign across them. According to Donquixote Doflamingo, the smilie symbol is a growing trend.