I wonder why 404, any relation to 4 being similar to the word "death" in Chinese?

My first guess would be that they at one point decided to use numbers to designate locations instead of names, to make it easier for them to be secret (eg "codenames"). Then at one point someone figured that actually, lets not just thoughtlessly increment the numbers, but pick random numbers between 1-1000 so we add even more confusion. Kind of like Seal Team 6 I guess.

Yes,4 sounds similar to death in Chinese. But 404 was just a coincidence.