Wormwood: the name of the star derives from its effect on the water; it turned the water sour and bitter, so that it killed many of those who drank it. Wormwood itself is a bitter drug, made from an aromatic plant (Artemisia absinthium). The drug is not poisonous, but passages like Jer 9.15; 23.15 show that it was considered poisonous. Where a proper noun is lacking for this plant, the generic word “Bitterness” or “Bitter Drug” may be used as the name of the star (see “bitter” at the end of the verse). “Harsh-Tasting Substance” is another possible translation.

The water in one third of all rivers and fountains became wormwood (or, as Good News Translation translates, “turned bitter”). In many languages it will be helpful to say “a third of the fresh water.” It is somewhat strange that not all the people who drank of the water died, only many of them.

Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .