Nobody knows for certain, but local tradition and historians share three popular stories.
1. Moga Singh Gill
The most common story says the town is named after Moga Singh Gill, a leading member of the Wadan Gill clan who settled here.
2. A son who brought peace
The Gill and Brar clans once fought over land. To make peace, a Wadan Gill man married a Sangar Brar woman. Their son was named Moga, and the new settlement took his name.
3. King Maues
Some historians link the name to Maues, an Indo-Scythian king who ruled this region in the 1st century BCE. "Moga" may be an Indian form of "Maues".
Whichever story you believe, Moga has carried its name for over 300 years.
Sources: moga.nic.in, Moga district court website, Wikipedia.