from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
RULE TO SHOW CAUSE. An order made by the court, in a particular case, upon
motion of one of the parties calling upon the other to appear at a
particular time before the court, to show cause, if any he have, why a
certain thing should not be done.
2. This rule is granted generally upon the oath or affirmation of the
applicant; but upon the hearing, the evidence of competent witnesses must be
given to support the rule, and the affidavit of the applicant is
insufficient.