Poor Wickfield is down in the doldrums: (UsingEnglish.com) in
the dumps, down in the mouth – feeling sad and lacking the
energy to do anything, filled with melancholy and despondency.
Not that I know if Dickens used the term, but he describes
Wickfield’s depression well with the following sentence: “When
he came in, he stood still; and with his head bowed, as if he
felt it.” Samuel Taylor Coleridge used it in Rhyme of the
Ancient Mariner. But whatever is a doldrum? To find out we must
turn to the sea. According to Wikipedia: The doldrums is a
colloquial expression derived from historical maritime usage for
those parts of the Atlantic Ocean and the Pacific Ocean affected
by the Intertropical Convergence Zone, a low-pressure area
around the equator where the prevailing winds are calm. The low
pressure is caused by the heat at the equator, which makes the
air rise and travel north and south high in the atmosphere,
until it subsides again in the horse latitudes. Some of that air
returns to the doldrums through th