If I understand you correctly you need to use a dictionary to provide the sort of lookup mechanism you want:
self.array1 = @[@"word", @"word2"].mutableCopy;
self.array2 = @[@"this goes with word1", @"this goes with the second word"].mutableCopy;
NSDictionary *dictionary = [NSDictionary dictionaryWithObjects:self.array2
forKeys:self.array1];
NSLog(@"%@", dictionary[@"word"]);
// Prints "this goes with word1".