What does the 'belt' Orochimaru and the Sound Four wear signify? The Sound Four wear a purple-colored type of belt or wrap around their waists:



Orochimaru, their master, also wore one:



Being some of the few ninja I have seen wearing one, does it have a formal name? What does it signify and does it relate or exist in real world fighting..? It feels almost sumo-ish, I think.
The belt they are wearing is generally referred to as an "obi."

The belt braided in the style of Shimenawa ropes, sacred Shinto ropes made by twisting together straws. It is hung horizontally to indicate a sacred Shintoism place such as praying hall or torii. 

The Wikipedia article (linked above) notes that:


  A variation of the shimenawa is used in sumo wrestling by yokozuna (grand champions) during their entrance ceremonies to denote their rank. This is because the yokozuna is seen as a living yorishiro (formally shintai), and as such is inhabited by a spirit.