Came up the Lagan in a bubble
Do you think I'm stupid? The Belfast version of 'I wasn't born yesterday'.
Heard in Down
One pint, is it? Do ye think I came up de Lagan in a bubble?

Shall I translate it into posh English for you, mucker?
Hail and well met. Here it is in posh English.
A single pint, you say? Do you take me for an innocent who floated up the River Lagan in a soap bubble?
Questions
What does came up the Lagan in a bubble mean in Ireland?
Do you think I'm stupid? The Belfast version of 'I wasn't born yesterday'.
Where in Ireland do people say came up the Lagan in a bubble?
People say came up the Lagan in a bubble in Down.
How do you use came up the Lagan in a bubble in a sentence?
“One pint, is it? Do ye think I came up de Lagan in a bubble?”
Updated
Same phrase, other counties
- Down (not in the dictionary)