Hookah tobacco is a San'Shyuum stimulant that is smoked via water pipe. Although the drug allows San'Shyuum extra focus and mental acuity for a short duration, later reactions to the drug can include an extreme headache. A quick-acting herbal tea is available to deal with the side-effects, produced by clerics.
Because it is not native to Earth, it is impossible that Hookah is actually related to true Earth Tobacco. Instead, it is likely just a substance with similar qualities.