A writ of Chancery given by the ordinary to keep an excommunicate in prison till he submitted to the authority of the Church. The writ, which is now obsolete, used to begin with “Significavit nobis venerabilis pater,” etc. Chaucer says of his Sompnour -
“And also ware him of a `significavit.' ”
Canterbury Tales (Prologue), 664.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894