Brennus or Brennos is the name of two Gaulish chieftains, famous in ancient history:
The Celtic Helmet from Satu Mare, Romania (northern Dacia), an Iron Age raven totem helmet, dated around 4th century BC. A similar helmet is depicted on the Gundestrup cauldron, being worn by one of the mounted warriors (detail tagged here). See also an illustration of Brennus wearing a similar helmet.
The Senones or Senonii were an ancient Gallic tribe dwelling in the Seine basin, around present-day Sens, during the Iron Age and the Roman period. The Senones remained an independent people, ruled by
Bronze coin with a bird, struck by the Senones (c. before 52 BC)