The interesting origin of an old saying

After posting a question on one of my favourite websites (Melbourne Freecycle Cafe) I now know the origin of the saying '.. must have killed a Chinaman'.

"Historically, as the Chinese have had a presence in Australia since colonial days, there was once great folk superstition attached to them. A sure sign of fortune was attributed to encountering a Chinese person as one engaged in a bet, and it was supposed that killing such an individual would lead to a disastrous run of bad luck.

Verb
must have killed a Chinaman
1. (Australian) Figurative explanation for bad luck one is suffering.

Usage notes
• This term may be considered offensive to Chinese. Because of negative historical connotations, the term Chinaman is no longer in appropriate use, and persists only in this expression or similar dated expressions.

Quotations

• 1925, L. M. Newton, The Story of the Twelfth: A Record of the 12th Battalion, page 132

  It appeared as though someone in the Battalion must have killed a Chinaman, as the weather continued rough and stormy, with strong wind.

• 1992, Maurice Shadbolt, Monday's Warriors, page 49

  'What troubles you?'

  'Luck. I must have killed a Chinaman. Or maybe broke a mirror.'

• 2004, Cycling News, 14 January 2004 link

  "The left hand side of my body has really been hammered the last six months; I must have killed a Chinaman in a previous life or something, I don't know," mused Vogels.

References

• "must have killed a Chinaman", in The New Partridge Dictionary of Slang and Unconventional English, Eric Partridge, page 393

• "I must have killed a Chinaman", in A Dictionary of Catch Phrases: British and American, from the sixteenth century to the present day, Eric Partridge & Paul Beale, page 218. "
  

http://en.wiktionary.org/wiki/must have_killed_a_Chinaman

We use or hear these old sayings and proverbs every day and more often than not never think about the origin so I've found it really interesting to learn the history behind this saying.