Get out the microscope, because we’re going through this poem line-by-line.
"And hast thou slain the Jabberwock?
Come to my arms, my beamish boy!
- The setting has changed again.
- Now the son is back at home, and the parental figure is speaking again.
- The parent asks what is probably a rhetorical question: did you kill the thing? Even though the hero comes back with the Jabberwock's head, and it seems quite obvious that the Jabberwock is dead.
- The word hast is an old form of have; thou is an older form of you; and slain is simply past tense of slay, which means "to kill."
- The parent then asks the son to give him a hug ("come to my arms"), and describes the son as beamish. This word isn't so hard: to beam means "to smile," specifically to smile emphatically. Which is probably what we'd be doing too, if we had just emerged victorious from a battle with evil.
O frabjous day! Callooh! Callay!"
He chortled in his joy.
- This is the first true evidence that we get that the parent is a father, because it's a "he" who is doing the chortling (which means "laughing") in the second line.
- Frabjous sounds a whole lot like fabulous, doesn't it? Maybe a combination of fabulous and joyous, just to get that "j" sound in there. And also because we know by this point that Carroll does love combining words.
- So what's up with the "callooh! callay!" part there? Well, it's probably something like the Wonderland-equivalent of "hooray!" and "yay!" – sounds similar, no? And, as with other things in this poem, sound is mostly what we have to go on.
- We can also safely assume that this is a moment of joy (it says so right there), so those associations make sense.