How did subpoena originate?: Information Roundup
subpoena is a writ commanding a person to appear before a court, grand jury or other judicial body to testify as a witness. The word is from Latin sub, "under," and poena, "punishment" or "penalty." The subpoena received its name from the fact that under English common law the person summoned in this manner was bound to appear "sub poena centum librorum," that is, "under a penalty of one hundred pounds."