Thanks all for the replies, the style itself predates Sikhism and has its roots within Hindu Kshatriya (warrior clan) history, who can predate their skills to ascetic orders, sadhus and yogis, going back further the Kapilkas and Pasupatis, who ultimately got their influence from the god of destruction Shiva. The art has been passed down to various orders over centuries, and currently the Nihang Singhs (Sikh warrior clans) are the custodians of this art.
The more ancient influence of this art is kept, with forms and techniques deriving from various Hindu Gods and Goddesses, to Varha, the first form of Vishnu who manifests as a wild boar, Sheshnaag the thousand headed cobra of Vishnu, Grur the chariot mythical bird of Vishnu, Narsingha, the lion incarnation of Vishnu, Nandi the bull of Shiva, Hanumaan langur monkey general of King Rama. These 6 form the basic levels of the art, which incorporate various fighting styles and ranges, from close combat strikers, to long distance strikers, others are grappling styles which prevent takedowns, and others which aim to take the opponent to the ground and stay up. Higher levels of the art are seen in the forms which take feminin inspiration from the Goddess Durga and Kalika, and the masculine inspiration is taken from Shiva and Mahakaal. All the above will be blended into an amalgamation of strategies, techniques, and styles which make up the purest of forms, Adhnarishwar or Sarbkaal, which blend the feminin and masculine together.
So even though the art is with the Sikhs, we acknowledge and accept its ancient roots, with the various forms taking seat alongside the Gurdevs (Masters) of the art.