In Greek mythology, Acarnan (Ancient Greek Ἀκαρνάν) is son of Alcmaeon and Callirrhoe daughter of Achelous, twin-avenger with Amphoterus of their father's murder, and eponymous colonizer of Acarnania. Distinct from the Dulichian suitor of Penelope who shares the name.
Adapted from Wikipedia, "Acarnan" · CC BY-SA 4.0
I.Avenger and eponym
After Phegeus' sons kill Alcmaeon, Callirrhoe prays that her infant sons grow at once. Acarnan and Amphoterus meet the murderers at Agapenor's house as they carry Harmonia's necklace toward Delphi, slay them, then kill Phegeus and his wife at Psophis. They dedicate the cursed heirlooms at Delphi and, from Epirus, lead settlers into the land called Acarnania after Acarnan.
Strabo and Apollodorus preserve the eponym strand that ties the western Greek ethnos to Alcmaeon's house.
II.Homonym care
Wikipedia also lists Acarnan among Penelope's Dulichian suitors (atlas id acarnan-dulichium). The id acarnan without suffix is Alcmaeon's son and land-eponym alone.