The convention adopted “high crimes and misdemeanors” with little discussion. Most of the framers knew the phrase well. Since 1386, the English parliament had used “high crimes and misdemeanors” as one of the grounds to impeach officials of the crown. Officials accused of “high crimes and misdemeanors” were accused of offenses as varied as misappropriating government funds, appointing unfit subordinates, not prosecuting cases, not spending money allocated by Parliament, promoting themselves ahead of more deserving candidates, threatening a grand jury, disobeying an order from Parliament, arresting a man to keep him from running for Parliament, losing a ship by neglecting to moor it, helping “suppress petitions to the King to call a Parliament,” granting warrants without cause, and bribery. Some of these charges were crimes. Others were not. The one common denominator in all these accusations was that the official had somehow abused the power of his office and was unfit to serve.
From High Crimes and Misdemeanors by Constitutional Rights Foundation