@Chrono79, @awesomead, thanks for your rapid answers, it was needed to type exactly as the author wrote:
"var firstName = {A: 'Alpha', B: 'Beta', C: 'Cache' ...}
var surname = {A: 'Analogue', B: 'Bomb', C: 'Catalyst' ...}"

So, "firstName" and "surname". Not "surName" as I typed.

I think it was javascript, in that case:

var surname = {A: 'Analogue', B: 'Bomb', C: 'Catalyst' ...}

it's surname not surName

Thanks for modifying your language :)

I'm assuming you're using Python. Python is a case-sensitive language. surName and SURNAME are two seperate names (variables, as you'd call them). The error you're getting hints at that.
The description states that the names of the preloaded dictionaries are SURNAME and FIRST_NAME.

Could be better! Marked by author as solved but keeps returning: "ReferenceError: surName is not defined". If the two arrays can not be loaded into code wars, then the author must put into the description, even if this occupy a lot of space. This way we can copy into work area in order to use them and solve with our code.

Wow! I had tottaly forgotten this math principle. This is a great and simple solution!