Wikipedia also uses the grand jury analogy.
"Impeachment in the United States is the process by which a legislature (usually in the form of the lower house) brings charges against a civil officer of government for crimes alleged to have been committed, analogous to the bringing of an indictment by a grand jury. At the federal level, this is at the discretion of the House of Representatives."
https://en.wikipedia.org/wiki/Impeachment_in_the_United_States