Plutarch Quaestiones Convivales 8.6.4

[4] Then Theon interrupting him said: By no means, if we must trust those who have delivered down to us the ancients’ way of living. For they say that those being used to work, and very temperate in a morning, ate a bit of bread dipped in wine, and nothing else, and that they called that meal ἀκράτισμα, from the ἄκρατον ( wine). Their supper they called ὄψον, because returning from their business they took it ὀψέ ( late). Upon this we began to enquire whence those meals δεῖπνον and ἄριστον took their names. In Homer ἄριστον and ἀκράτισμα seem to be the same meal. For he says that Eumaeus provided ἄριστον by the break of day; and it is probable that ἄριστον was so called from αἴριον, because provided in the morning; and δεῖπνον was so named from διαναπαύειν τῶν πόνων, easing men from their labor. For men used to take their δεῖπνον after they had finished their business, or whilst they were about it. And this may be gathered from Homer, when he says, But some perhaps will derive ἄριστον from ῥᾷστον, easiest provided, because that meal is usually made upon what is ready and at hand; and δεῖπνον from διαπεπονημένον, labored, because of the pains used in dressing it.