... 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 ...

For the more than 200 years since the Constitution was adopted, Congress has seriously considered impeachment only 18 times. Thirteen of these cases involved federal judges. The “high crimes and misdemeanors” that the House charged against these judges included being habitually drunk, showing favoritism on the bench, using judicial power unlawfully, using the office for financial gain, unlawfully punishing people for contempt of court, submitting false expense accounts, getting special deals from parties appearing before the court, bullying people in open court, filing false income tax returns, making false statements while under oath, and disclosing confidential information ...

https://www.crf-usa.org/impeachment/high-crimes-and-misdemeanors.html