The word "Vishu" is likely derived from the Sanskrit word "Vishuva", which means "equinox".
Here's why this is relevant:
* Vishu festival: The Vishu festival in Kerala is celebrated on the first day of the Malayalam calendar month of Medam (typically falls in mid-April). This is close to the vernal equinox, the time when day and night are of equal length.
While "Vishu" itself isn't Sanskrit, its origin lies in a Sanskrit word that denotes an astronomical event.