Q: The suffix “pre” usually means before and “pro” usually means for. So what has happened etymologically to “prescribe” and “proscribe,” which essentially mean for and against.
A: We adopted “prescribe” in the 15th century from the Latin praescribere (meaning, among other things, to inscribe on the front, write beforehand, or lay down rules).
The term meant to lay down rules or make a ruling when it first showed up in English in 1445 in the records of St. Bartholomew’s Priory, according to citations in the Oxford English Dictionary.
It wasn’t until the 16th century that “prescribe” took on its medical sense. The Dutch humanist Erasmus used it in 1533 when he prescribed that a man in danger of dying should read a medical tome by Jacobus de Partibus (a k a the Parisian scholar Jacques Despars).
The term was soon being used to prescribe medicine as well as medical reading, as in this excerpt from a 1581 translation of an Italian treatise on etiquette: “I prescribe for his health this medicine.”
As for “proscribe,” we adopted it from the Latin proscribere (meaning, among other things, to announce publicly or record in writing).
In ancient Rome, according to the OED, “proscription consisted in the publication of the names of citizens who were declared outlaws and their goods confiscated.”
When the term first showed up in English in 1445, it meant to publish or announce publicly the name of someone condemned to death, imprisonment, exile, banishment, or some other punishment. Now, that’s strong medicine.
The first OED citation is from John Lydgate’s poem “Queen Margaret’s Entry into London,” which refers to exiles “of wrecched tirannye” who “were proscribed.”
In the 17th century, “proscribe” took on its modern sense of prohibiting, excluding, or declaring unacceptable.
In fact, the first citation in the OED for this usage, from a 1622 English translation of a Spanish novel, uses both the terms you’ve asked about: “Lord, that prescribes, and proscribes / Lawes at his pleasure.”