What is "laeti"

Laeti , the plural form of laetus , was a term used in the late Roman Empire to denote communities of barbari (" barbarians") i.e. foreigners, or people from outside the Empire, permitted to settle on, and granted land in, imperial territory on condition that they provide recruits for the Roman military. The term laetus is of uncertain origin. It means "lucky" or "happy" in Latin but may derive from a non-Latin word. It may derive from a Germanic word meaning "serf" or "half-free colonist". Other authorities suggest the term was of Celtic or Iranian origin.