Harbinger \HAR-bing-uhr\ , noun;
1. A person who goes ahead and makes known the approach of another; herald
2. Anything that foreshadows a future event; omen; sign
3. A person sent in advance of troops, a royal train, etc., to provide or secure lodgings and other accommodations
4. To act as harbinger to; herald the coming of.
Dating to the late 15th century, this word originally referred to "one sent ahead to arrange lodgings" for a monarch, an army, etc. and it was spelled herbengar. It is an alteration of Middle English herberger "provider of shelter, innkeeper". The Middle English word dates to the late 12th century and comes from Old French herbergeor, which evolved from herber ("lodging, shelter") via herbergier ("provide lodging"). Herber is derived from Frankish *heriberga ("lodging, inn").
I've been reading "Decision Points" by George W. Bush and this seems to be a favorite word of his. He says something like, "this was a harbinger of things to come" quite a bit. The first time I saw it I had to look it up because I had never seen or heard this word before, but his (over?) use is really ingraining this word into my vocabulary.