福

The character above is shown upside down. At New Year's it is common to hang "fu" upside down because the word for "upside down" is a homophone for "arrived," the hope being that "fu" will arrive at your door.

- from The Useless Tree

The character 福, of course, means "good fortune," "good luck," "prosperity." A full explanation of the origin of the character may be found here. Yet there is another translation and meaning which makes it appropriate for anyone of the Christian religion - Fu/福 is the standard character used to translate "grace" in Christian texts. The first line of the 'Ave Maria'/'Hail Mary' prayer (and naturally, also Gabriel's greeting) is 萬福馬利亞,主與妳同在 - which literally may be translated as "O ten-thousand fortuned Mary, the Lord is with thee".

So, if the character 福 means 'grace' as well, then perhaps any Christians of Chinese ancestry may think it doubly appropriate to have the character 福 upside-down in their houses, thus giving the meaning 'may grace arrive'.

- from Edward