The doldrums are a spell of low spirits or of no progress. In the doldrums all winter.
The word first named the belt of calm near the equator where sailing ships could sit for weeks. It always takes the and is always plural, which is unusual even for an English idiom.
1noundoldrumsA spell of low spirits or of no progress.
“The whole trade was in the doldrums for three years.”
doldrums is a period.