Which weather pattern's name means 'the boy child' because it arrives near Christmas?

El Niño, named by Peruvian fishermen for the warm current that appears off the coast around Christmas - the boy child being the infant Jesus. In strong years it does not go away in the new year, and the fishery collapses because the warm surface layer cuts off the cold nutrient-rich upwelling the anchovies depend on.

It is one half of a seesaw. The trade winds normally pile warm water in the western Pacific; when they slacken it sloshes back east, and the whole pattern of where the ocean is warm - and therefore where the rain falls - shifts across a third of the planet. La Niña is the opposite phase. Consequences are global and reliable in direction if not in size: drought in Australia and Indonesia, floods in Peru, a quieter Atlantic hurricane season.

The 1876-78 event is the grim case. Monsoon failure across India, China and Brazil coincided with colonial policies that kept exporting grain from famine regions, and deaths ran into the tens of millions. El Niño has been implicated in the timing of famines, epidemics and conflicts across several centuries, which is why forecasting it a season ahead is worth as much as it is.