It turns out that tetraphobia (or the fear of the number 4) is an east Aisan superstition. The word for 'four' in Chinese, Taiwanese, Vietnamese, Korean and sino-Japanese is similar or identical to the word for 'death'. Consequently, they avoid use of numbers with 4 in it, including building levels and especially on festive holidays.
Some hotels even go as far as removing rooms 14 &24 because '14' sounds like 'die for sure' and '24' sounds like 'easy to die'. Restaurants may even remove any table numbers with a 4 in it.
Thinking back on it, I'm pretty sure that I have stayed on the 'death floor' at some stage during the year.