beļģis

Etymology
Borrowed from, the name of a group of Gallo-Germanic tribes living in the area of present-day Belgium, apparently from , , i.e., originally this tribal name would have meant “the people who swell with anger or battle fury.”

Noun

 * 1) (male) Belgian (i.e., a man born in Belgium)
 * 2)  Belgian; pertaining to Belgium and its people
 * 1)  Belgian; pertaining to Belgium and its people

Usage notes
The two synonyms and, when referring to an individual from Belgium, appear to be fully interchangeable. In the plural, is much more frequently used than.