Cuid a dó
I have been watching some TG4 and two shows have the phrase "cuid a dó" as they are going into the later part of the show. What does this phrase mean in that context? 5 , 2

Question

Answer

It means "part 2". 
"Cuid" means "part"; "dó" is the form of the numeral "two" used in counting (the non-adjectival form); and "a" has no meaning by itself, it's a particle which is placed before non-adjectival numbers.
Don't confuse "cuid" with "cúig", meaning "five".