That etymology just shows it had a w in it originally. It must have taken part in the w-colouring that means word and lord, ward and hard don't rhyme, whenever that was (1500s?), since the word "sward" exists and has the expected "or" vowel as in "ward", and "sword" didn't collapse into it, so must have become something like "swurd" to rhyme with curd.

Then the w must have been lost after that, but before er and ur and ir became the same, since it still exists in swerve and swirl.