During their first confrontation, Sarah Jane pointed out that the name Wormwood appears in the Bible. It is mentioned in the Book of Revelations as a star that crashes into the Earth and poisons its waters. From the knowing look on Mrs. Wormwood's face, I'm under the impression that she chose the name deliberately. It makes sense, as she came down from the heavens and tried to infect the human population with the Bane genetic material via the soft drink Bubble Shock.
Here's what Wikipedia had to offer about the Biblical version of "Wormwood":
It's only clear reference as a named entity occurs in the New Testament book of Revelation: "And the third angel sounded, and there fell a great star from heaven, burning as it were a lamp, and it fell upon the third part of the rivers, and upon the fountains of waters; And the name of the star is called Wormwood: and the third part of the waters became wormwood; and many men died of the waters, because they were made bitter." (Revelation 8:10, 11)
Certain commentators have held that this "great star" represents one of several important figures in political or ecclesiastical history, while other Bible dictionaries and commentaries view the term as a reference to a celestial being.
A Dictionary of The Holy Bible states, "the star called Worm wood seems to denote a mighty prince, or power of the air, the instrument, in its fall, of sore judgments on large numbers of the wicked." Scofield Reference Notes draws a link between the term in Revelation and Isaiah 14:12, which reads, "How you have fallen from heaven, O morning star, son of the dawn! You have been cast down to the earth, you who once laid low the nations!"