"Don't drive or operate heavy machinery": FDA-required? History of wording?

In subject: The boilerplate warning for zillions of medications, even OTC ones (I think) like antihistamines.

Drug-release information specifications for prescribers and consumers is a hugely regulated process, with enormous implications and even financial impact, and is negotiated by the pharm legal department; a debate about even having a “black box” warning for anti-depressants, let alone the wording, made the NYTimes.

So:

  1. Is there an identifiable history and record of exactly that wording?
  2. If so, I’m particularly interested in what the definition/decision of “heavy machinery.” Any ideas?