ESTRAGON
What exactly did we ask him [Godot] for?
VLADIMIR
Were you not there?
ESTRAGON
I can't have been listening.
VLADIMIR
Oh . . . Nothing very definite.
ESTRAGON
A kind of prayer.
VLADIMIR
Precisely.
ESTRAGON
A vague supplication. (1.202-8)
In case you didn’t catch the GOD inside his name, Beckett gives some hints that GODot has something to do with GOD. Case in point, this line here, where Estragon says they have offered a prayer to Godot. The problem is, they don’t seem to know exactly what they’ve prayed for. In a way, this exchange mocks religion for its inherent uncertainty.
ESTRAGON
To try him with other names, one after the other. It'd pass the time. And we'd be bound to hit on the right one sooner or later.
VLADIMIR
I tell you his name is Pozzo.
ESTRAGON
We'll soon see. (He reflects.) Abel! Abel!
POZZO
Help!
ESTRAGON
Got it in one!
VLADIMIR
I begin to weary of this motif.
ESTRAGON
Perhaps the other is called Cain. Cain! Cain!
POZZO
Help!
ESTRAGON
He's all humanity. (2.619-626)
OK, this passage can be confusing. We had to read it a few times. Estragon thinks that if they call Pozzo by the correct name (presumably, it isn’t "Pozzo"), he will answer them. He guesses "Abel" and is delighted to see that he got it right on his first try. When he says "Perhaps the other is called Cain," he’s talking about Lucky. Unfortunately, Pozzo also responds to the name "Cain," prompting Estragon to remark that Pozzo is all of humanity—he would therefore answer to any name.
Now for the religious stuff: in the Bible, Cain and Abel are the sons of Adam and Eve. One day, they both make sacrifices to God, but for some reason (and here’s what the play is getting at regarding the random and illogical nature of religion) God accepts one sacrifice (Abel’s) and rejects the other (Cain’s). This leads to Cain sitting Abel down and having a conversation about his feelings. No, wait, it leads to Cain killing Abel in a fit of jealousy, which in turn leads to God punishing Cain. Just note that Cain and Abel are yet another pair, much like the two thieves crucified with Jesus. Coincidence? Probably not.
ESTRAGON
And if we dropped [Godot]? (Pause.) If we dropped him?
VLADIMIR
He'd punish us. (2.848-9)
Vladimir doesn’t know anything about Godot—what he looks like, who he is, and he even if Godot's really his name. Yet Vladimir seems undeniably certain about his fear, which means he is certain of Godot’s power, if nothing else.