Did the Ring Need a Label?

[Inziladun]

We all know of the inscription on the One Ring, written in Elvish letters, in the Black Speech:

One Ring to bring them all and in the darkness bind them.

Gandalf tells Frodo that that particular line was part of a verse "long known in Elven-lore".

Now, that verse was written by Elves, presumably in response to their awareness of Sauron's motives behind the fashioning on the Rings of Power. And Gandalf later says during the Council of Elrond that:

'Out of the Black Years come the words that the Smiths of Eregion heard, and knew that they had been betrayed:

One Ring to rule them all, One Ring to find them, One Ring to bring them all and in the Darkness bind them.'

So, the wearers of the Three seem to have either physically or psychically "heard" Sauron himself speaking those words, at which time his plot was revealed.

Maybe Sauron was obliged to speak that incantation, for some reason, to "activate" the One. Question is, why was it necessary to make any inscription on it, and those words in particular? Was Sauron afraid he might not be able to recognize it if he took it off before he got into the bathtub?
He seems to have not considered the possibility that he could one day lose the One, and at any rate he should easily have been able to tell by his own connection with it whether he held it or not. What was the purpose of labeling the One like that?