licit

Licit is far less common than its antonym illicit, but you probably won't be surprised to learn that the former is the older of the two. Not by much, though: the first known use of licit in print is from 1483, whereas illicit shows up in print for the first time in 1506. For some reason illicit took off while licit just plodded along. When licit appears these days, it often modifies drugs or crops. Meanwhile, illicit shows up before words like thrill and passion (as well as gambling, relationship, activities, and, of course, drugs and crops.) The Latin word licitus, meaning "lawful," is the root of the pair; licitus itself is from licēre, meaning "to be permitted."