"George has shorts."
Translation:Tha briogais ghoirid aig Seòras.
It's ghoirid. Ghoiraid wouldn't be a possible spelling (at least it would be a very unlikely spelling) in Gaelic. Gaelic divides vowels into broad (a, o, u) and slender (e, i). The quality of vowel (whether broad or slender) determines the quality of the consonant (broad or slender) that it comes before or after. The rule is that a consonant in the middle of a word has to be surrounded by vowels of the same quality (i.e. the vowels on either side of a consonant don't have to be the same vowels, but they have to be either both broad or both slender).
As the i before the r indicates that the r is slender (the r sound you sometimes hear on the recordings almost like a th sound), the r also has to be followed by a slender vowel, here an i. That second i before the d indicates that the d is also slender - pronounced like a tch sound rather than a broad d, which sounds like flabby cross between a d and a t.
That explains some of what look like unnecessary vowels in Gaelic spelling but which turn out to be quite logical (there is a very small number of exceptions to this rule).