Also, The manx accent is similar though different to Liverpudlian, and I suspect a play on words with the whack and wack - whack meaning to hit something ans wack being a friendly term for another person, just as one may say 'you alright mate?' they would say 'you alright wack?'
Whatever it all means, it's a grea song about a great place! The Crack has always been 90+ (special significance to Douglas motorcycle owners!) when I've been there!