In Homer's Odyssey, Arnaeus — nicknamed Irus because he ran messages like Iris — is the resident beggar of Ithaca who challenges the disguised Odysseus in Book 18. The suitors stage a fight for food and a place at their table; Odysseus knocks him out with a blow under the ear and drags him to the courtyard. Distinct from Irus son of Actor, father of the Lapith Eurytion.
Adapted from Wikipedia, "Arnaeus" · CC BY-SA 4.0
I.Fight in the hall
Irus insults the new beggar as a rival for scraps. Antinous promises the winner food and a seat with the suitors, and threatens that the loser will be sent to King Echetus the maimer. Athena makes Odysseus look larger; Irus falters, then throws a punch. Odysseus, choosing not to kill him and spoil the disguise, crushes his jawbone, hauls him outside, and sets him against the wall to scare off dogs and pigs.
The episode sharpens Homeric themes of hospitality abused and appearance versus reality: the "beggar" is the returning king, while Irus — the house's own beggar — is cast out.
II.Homonym
Mythographic lists also know an Irus son of Actor, father of Eurytion (whom Peleus accidentally kills) and of Eurydamas. Atlas id irus-beggar is only the Ithacan Arnaeus of Odyssey 18.