Aha... Thanks, bianca ... What do you mean (when you say it must be a good joke if you understand it)? Why does it make no sense?
Do I understand the joke well?
1st speaker: My wife's gone to the West Indies.
2nd speaker: Jamaica? (Did you make her (... go there??) ?)
1st speaker : No, she went of her own accord. (No, she went voluntarily.)
Exactly! You got it!
Just like 'kangaroo', 'Jamaica' is a sound immitation word or onomatopeic.