I wanted to add stuff to this thread. It isn't exactly the same thing, but "Tantric Sex" comes from the Tibetan form of Buddhism. The idea is mind over body, which allows one to control their own orgasm. It can also come from the idea of Tantric meditation from Hinduism which is again the control of mind over body. The idea is that a person should indulge in the pleasures of the physical world in order to let go of the attachment to the earthly pleasures.

In both cases this can draw a parallel to some bdsm play with control and/or the desire for longer and/or meaningful sex. To control the mind and body and let go of the attachment to pleasure, you learn more about yourself and your limits.

Time for my 2 cents: The sort of Tantric sex talked about by erotic writers is sort of a bastardization of Tantrism. It is like the kind of yoga people do for exercise. Sure, it is good for that, but it isn't what it is for. Yoga is a sort of meditation and prayer done with the whole body. Thoughts, breathing, movements of the arms, placing of the fingers, etc. are all involved to complete "mindful meditation". This sort of meditation is a homage to the gods and a way to control the mind and body to reach liberation.