Q: You wrote in 2008 and 2007 about words that have totally opposing – or at least wildly differing – meanings. For example, “sanction “and “cleave.” By what etymological process do these words develop? Perhaps the language deities have a sense of humor.
A: These two-faced words are usually called “contronyms,” though they are sometimes referred to as “auto-antonyms,” “self-antonyms,” or “Janus words” (after the god with two faces).
In addition to “sanction” (to approve or penalize) and “cleave” (to cling or part), some others are “screen” (to view or hide from view), “bolt” (to flee or fix in place), and “weather” (to stand up to stress or be eroded by stress).
Each of these words (and there are many more) developed its opposing meanings for different reasons.
In the case of “cleave,” it comes from two distinct verbs with different roots in Old English. The one (cleofian or clifian) meant “cling” or “stick,” and the other (cleofan) meant “split” or “divide.”
The two eventually merged in spelling and pronunciation, and the differing meanings were preserved.
In the case of “sanction,” the verb originally meant to ratify or confirm by enactment. A little later this came to mean to permit; still later it grew to mean to enforce by imposing penalties.
The verb followed the much earlier noun, which first meant a law or decree and later meant a penalty.
Etymologically, according to the Oxford English Dictionary, it may be an adaptation of the Latin sanctionem (“action of ordaining as inviolable under a penalty, also a decree or ordinance”).
In the 17th century, the noun “sanction” was “extended to include the provision of rewards for obedience, along with punishments for disobedience, to a law,” the OED says.
So in looser senses it grew to mean encouragement or support on the one hand, and coercive measures on the other.
Such are the ways of language!