Cratylus (419)

Socrates. But it does not, if you employ the ancient word, which is more likely to be right than the present one. You will find that it agrees with the previous words for good, if instead of the epsilon you restore the iota, as it was in old times for διόν (going through), not δέον, signifies good, which the name-giver praises. And so the giver of names does not contradict himself, but δέον (obligation, right), ὠφέλιμον (useful), λυσιτελοῦν (profitable), κερδαλέον (gainful), ἀγαθόν (good), ξυμφέρον (advantageous), and εὔπορον (prosperous), are plainly identical, signifying under different names the principle of arrangement and motion which has constantly been praised, whereas the principle of constraint and bondage is found fault with. And likewise in the case of ζημιῶδες, if you restore the ancient delta in place of the zeta, you will see that the name, pronounced δημιῶδες, was given to that which binds motion (δοῦντι τὸ ἰόν).

Hermogenes. What of ἡδονή (pleasure) and λύπη (pain) and ἐπιθυμία (desire), and the like, Socrates?

Socrates. I do not think they are at all difficult, Hermogenes, for ἡδονή appears to have this name because it is the action that tends towards advantage (ἡ πρὸς τὴν ὄνησιν τείνουσα); the delta is inserted, so that we say ἡδονή instead of ἡονή. Λύπη appears to have received its name from the dissolution (διάλυσις) of the body which takes place through pain. Ἀνία (sorrow) is that which hinders motion (ἰέναι). Ἀλγηδών (distress) is, I think, a foreign word, derived from ἀλγεινός (distressing). Ὀδύνη (grief) appears to be so called from the putting on of pain (τῆς ἐνδύσεως τῆς λύπης). Ἀχθηδών (vexation) has a name, as anyone can see, made in the likeness of the weight (ἄχθος, burden) which vexation imposes upon motion. Χαρά (joy) seems to have its name from the plenteous diffusion (διάχυσις) of the flow of the soul. Τέρψις (delight) is from τερπνόν (delightful); and τερπνόν is called from the creeping (ἕρψις) of the soul, which is likened to a breath (πνοή), and would properly be called ἕρπνουν, but the name has been changed in course of time to τερπνόν. Εὐφροσύνη(mirth) needs no explanation, for it is clear to anyone that from the motion of the soul in harmony (εὖ) with the universe, it received the name εὐφεροσύνη, as it rightfully is; but we call it ευφροσύνη. Nor is there any difficulty about ἐπιθυμία (desire), for this name was evidently given to the power that goes (ἰοῦσα) into the soul (θυμός). And θυμός has its name from the raging (θύσις) and boiling of the soul.