In each pair, the first word begins with an unvoiced consonant and the second word begins with the voiced version of the same consonant.

In English, the regular way to form the plural is by tacking on the sibilant consonant “s”. That’s true after an unvoiced consonant, like “cat” and “cats”. After a voiced consonant, we pronounce the voiced sibilant consonant “z” but use the letter “s”: “dog” and “dogs.”

Thus, “cordz” is an intentional misspelling that in fact represents English pronunciation in an easier-to-understand way than standard orthography, like “nite” and “night.”