what does the phrase headsup me as in...'i will give you the headsup' to mean i will bring you up to speed (I reckon). when did this start and how did it come about
It means to give a warning, it probably dates back to the days when archers were in use, and the cry of 'Heads up!' would go out, so people could see the arrows coming and hopefully avoid them.
If the archer theory were true then the phrase would have been in widespread use throughout the centuries but I first heard it in the mid-90s. So, unless US business (and I think that this stems from the US) is populated by a mass of toxophiles, I don't think this is the answer. It's a question that's intrigued me though, but then so has "pushing the envelope" - what's that all about?