"Speak of the Devil"

I was at a meeting at work today and someone was being talked about, and they suddenly walked in! Someone said "speak of the devil!" and I have heard of that before, but thanks to Forrest, I thought I would look up the origins of this rather scandalous phrase:

From http://www.phrases.org.uk/meanings/speak-of-the-devil.html

This phrase is used to acknowledge the coincidence of someone arriving at a scene just at the time that they are being talked about. Clearly, nothing sinister is implied by this and it is just a jokey way of referring to the person's appearance. In fact, many people using the phrase might not be aware that, prior to the 20th century, the term wasn't meant lightheartedly at all. The full form goes like this - "speak of the Devil and he will appear". The phrase originated in England, where it was, and still is, more often given as 'talk of the Devil'.
The phrase is old and appears in various Latin and Old English texts from the 16th century. The Italian writer Giovanni Torriano has the first recorded version in contemporary English, in 'Piazza Universale', 1666:
"The English say, Talk of the Devil, and he's presently at your elbow."
Also, in 'Cataplus, a mock Poem', 1672 - re-printed in Hazlitt's Proverbs
"Talk of the Devil, and see his horns."
These both imply that the term was widely known by the mid-17th century. It enshrined the superstitious belief that it was dangerous to mention the Devil by name. This prohibition was strong, like the prohibition on speaking the name of God. The numerous synonyms for the Devil - Old Nick, Prince of Darkness, the Horned One etc. are no doubt a consequence of this.
People may not have believed that the mention of the Devil would cause him to actually appear. Shakespeare, for example, uses the term quite often. In The Comedy or Errors:
"Marry, he must have a long spoon that must eat with the devil."
Nevertheless, an open reference to the Devil or the occult was considered, at the very least, unlucky and best avoided. This belief was reinforced by the clergy. Richard Chenevix Trench, Dean of Westminster, 1856-63, wrote:
"'Talk of the devil and he is bound to appear' contains a very needful warning against curiosity about evil."
The original phrase began to lose its power during the 19th century. By then it began to appear as a homily warning against eavesdropping, as here from the Stevens Point Journal, Wisconsin, February 1892:
"No good of himself does a listener hear,Speak of the devil he's sure to appear"
The migration away from anything sinister, or even serious, continued when the phrase was taken up as an Ozzy Osbourne album title. The record company did hold with literary tradition though, by issuing it as 'Talk of the Devil' in the UK.