What's the origin of Govinden festival...

Different people will have different things to say about Govinden.

The root of the festival is actually debatable. Some believe it is an equivalent of the Govardhana Puja, others claim that it was a way devised by our ancestors while they were still under colonisation to gather the community together and make sure rites and rituals were not lost. Still others believe it is a purely Vaishnavite festival.

Source : Bansuri Blog

The blog referenced above gives a good description of the festival, so please check it out. All I know is the Tamils & Telegus in Mauritius celebrate this from mid September to mid October, a 1 month period, during which they fast for Lord Krishna.