This morning Ruth pointed out an obvious etymology that I'd somehow never noticed before:
difficult is essentially
dis- +
facile (though it's slightly more complicated than that). It's a little more obvious in Spanish or French, where the words are
fácil/facile and
difícil/difficile. (She made the connection while doing a Duolingo lesson in Spanish.)
The word
facile isn't as common in English as
easy, and it usually means something that was not just easy but shallow or simplistic in some way.
Facile comes from the root of the Latin verb
facere "to do" plus the suffix
-ilis, which forms what Wiktionary calls "
an adjective noun of relation, frequently passive, to the verb or root." In simpler terms,
facilis meant "doable" or "easy to do".
Difficult has a slight more convoluted history. Wiktionary says that it was backformed from
difficulty, which was borrowed from the Old French
difficulté, which came from the Latin
difficultas.
Difficultas is essentially
difficilis plus the sufffix
-tas, which forms abstract nouns (like the English suffixes
-hood or
-ness). And
difficilis is just
dis- plus
facilis. So
difficulty is basically the state of being not easy or not doable.