Catherine Tate Show (Nan) Question?

Question

Basically, there is an phrase of Nan's Sketch on Catherine Tate which i dont understand the joke of.

Nan's TV broke down, and an electrician came round who was named, Danny Shaw. Nan knows his mother Lou Shaw, who she refers to as "Loopy F*cking Lou".
Nan offers £50 to Danny Shaw, and he reluctantly accepts. When Danny leaves, obviously Nan slags him off to her Grandson, saying:

NAN: I remember when he was little, he used to come up here wearing his little cowboy outfit...He should have f*cking kept it on!!

I dont understand the joke when she says "He should have f*ucking kept it on!!"
Someone explain?

Answer 1

It means he's a cowboy lol and you know what that means (he will rip you off)

Answer 2

Ever heard of a cowboy builder. Its a person who does rubbish work for lots of money.

Answer 3

Cr*p tradesmen are called cowboys. Obviously she is implying that he is cr*p at what he does.

Answer 4

Yes its very funny i love the granny.

Answer 5

ha, i wanted to know the same thing.

Sorry, i don't know "/.