Many different techniques are evolved over time. But Firstly they were inspired by Carpets.
The Anotolian people were exceptionally skilled in carpet weaving and they transferred those skills to produce tri dimesion fabricscarpets.
Basically the They used 2/2-twill weave construction and They were used thin rods made ​​of dogwood tree to create a pile on the fabric.
This created a unique towel which had loops and piles of threads that would be standing up on the surface of the cloth.
In fact the towels that are used all over the world today were first woven in Bursa back in the 18th century.
The single most important feature that contributed to the success of Turkish towels was the fact that they would be meticulously woven by hand.
A single weaver would only be able to produce a maximum of 4 towels in a day, which made them exclusive items.
*"In the late 1840’s Henry Christy returned to England from Constantinople with a sample of looped pile fabric, which was new to the Western World. By 1851 his brother Richard had created the first mechanical loom to produce this remarkable cloth. Thus was born the first industurial terry towel." *(article taken from the owner's web site)
The history of Turkish towels seems to connect it with the practice of velvet weaving which was initiated in Bursa. (The carpet manufacture technics are another source of inspirations to terry velour products also)