What are Doldrums? Why are they called so?

A zone of low pressure lying parallel to equator where North-East and South-East trade winds converge and meet each other, producing calm and light surface winds and a strong upward movement of air is called Doldrums.

It is called so because the word Doldrums is associated with a gloomy, listless mood, perhaps reflecting the sultry air and variable breeze found there.