A cigarra was a mild narcotic that could be smoked for pleasure, relaxation, cancer, and death. They were completely different from death sticks because, (A) cigarras only killed over the course of decades of use, and (B) death sticks made people look like crazy homeless murderers, while cigarras made people look suave and debonair. Lando Calrissian was an avid smoker because playing sabacc without a smoke-filled room just felt wrong somehow.
Cigarras were made from dried vegetable matter that was discovered roughly 5000 BBY by noted Sith explorer Darth Walter Raleigh, who received leaves and smoking papers from the terrified natives of the worlds he conquered. The discovery of marijuana came later, when Gungan explorers started hanging out on these same conquered planets.