Myrrh is the aromatic gum resin of thorny Commiphora trees of the dry Horn of Africa and southern Arabia, tapped from the bark and hardened into reddish tears. Its name goes back to a Semitic root for bitter, and bitterness, of taste and of association, runs through its uses. It was one of the great commodities of the ancient incense trade that ran up western Arabia, costly and far-travelled, and it was burned as incense, compounded into perfume and medicine, and used in embalming. Pliny describes the trade and the many grades of the resin at length.
The exact botanical source of ancient myrrh remains genuinely debated: Commiphora myrrha is the principal commercial species today, but classical writers describe a trade dominated by Commiphora erythraea, and some scholars argue the myrrh named in the Hebrew Bible is better matched to yet another species, Commiphora guidottii, so that ancient myrrh may not correspond neatly to any single modern species and the trade name has likely covered several related resins across different periods. Modern genetic testing of myrrh sold in the international market has found that only a small fraction of commercial samples, in one study as few as eight per cent, reliably matched the species specified by current pharmacopoeias, showing the ancient confusion has never been fully resolved even by contemporary trade regulation.