doldrums

Almost everyone gets the doldrums—a feeling of low spirits and lack of energy—every once in a while. The doldrums experienced by sailors, however, are usually of a different variety. In the early-19th century, the word once reserved for a feeling of despondency came to be applied to certain tropical regions of the ocean marked by the absence of strong winds. Sailing vessels, reliant on wind propulsion, struggled to make headway in these regions, leading to long, arduous journeys. The exact etymology of doldrums is not certain, though it is believed to be related to the Old English dol, meaning "foolish"—a history it shares with our adjective dull.