This is not even getting to that; but that is actually pretty simple, to be fair. The negation is: 非常道 非 -- fei, this has been a negator for a very long time

This is not even getting to that; but that is actually pretty simple, to be fair. The negation is: 非常道 非 -- fei, this has been a negator for a very long time in Chinese 常 -- chang, this means something like common, usual, normal, or nominal (I suspect that translating this as "eternal" is a creative move on the part of some westerner) 道 -- dao, the way again Nowadays, 非常 as a compound is used to mean "extraordinary" ("not normal", "exceptional"); but it is not hard to see how it might be taken to negate 道 here.