Bob recited,
Aaron's rod, a.k.a Aaron's beard
May be cultivated or reared
throughout Eurasia
a scrophulariaceous
plant, by some gardeners revered.

That fancy word made me think of scrophula or scrofula. There must be a connection, but I don't know what connection there would be between the plant and the disease. Any ideas?

Well, scrofula comes from a Latin word scrofulae (pl.) meaning a swelling of the glands, which is a diminutive of scrofa 'sow', originally from the root *sker-. The funny thing about the variant spelling in English, scrophula, is that the -ph- tries (incorrectly) to show a Greek origin. Interesting thing about the common name for the scrophulariaceous plants: figwort. The fig refers to piles.

From "Stearn's Dictionary of Plant Names for Gardeners: A Handbook on the Origin and Meaning of the Botanical Names of some Cultivated Plants", William T. Stearn, first published in the UK by Cassell, 1992, reprinted in paperback with some "emendations" by Timber Press, 1966 and 2002:

"Scrophularia f. [feminine] Fig-wort. L. scrofule, scrophula, which it was supposed to cure. SCROPHULARIACEAE."

The Doctrine of Signatures, touted by Paracelsus, Jakob Böhme (1575-1624), Culpepper and others, says that all plants have healing powers which are somehow revealed in their morphology. The small reddish-brown flowers of the figwort resembled hemorrhoids ("figs"); therefore the plant must be usefull in treating them. Wort is from Old English wyrt, meaning plant, specfically an herbaceous medicinal plant. Figworts were also used to treat scrofula.

Wikipedia says Doctrine of Signatures refers to two separate concepts. I think one is really an extension of the other.

Tinman