This splendid word deserves to be better known, since it describes one of those eternal human states — dullness or lethargy — for which another good descriptor always comes in handy. It has been around since the seventeenth century in a rather poetical or literary way.
It derives from Latin hebet–, the stem of hebes, blunt or dull (so it is unconnected with the Greek goddess Hebe, whose name comes from the Greek word for puberty or adolescence). The Romans used their word for the state of knife blades and the like, but also for somebody who was dull or stupid. In English it has always had this figurative meaning. The noun’s heyday began in the nineteenth century and it is still going strong among those writers who like to extend their readers’ word power. It is also a term in psychology for apathy and emotional dullness.
It was a favourite word of Joseph Conrad, as in Nostromo: “From that solitude, full of despair and terror, he was torn out brutally, with kicks and blows, passive, sunk in hebetude”. It made an appearance in August 2001 in the columns of The Washington Post: “Too many Americans slouch toward a terminal funk of hebetude and sloth”
There are several related words, now rare, including the adjective hebetudinous, the abstract noun hebetudinosity, dullness or obtuseness, and the verb hebetate, to make dull or blunt.