pray in aid Old form(s): ayde
[legal] claim the assistance of someone who has a shared interest in a defence action
AC V.ii.27[Proculeius to Cleopatra, of Caesar] A conqueror that will pray in aid for kindness, / Where he for grace is kneeled to [i.e. he will ask you to help him to be kind to you]
SHAKESPEARE'S WORDS © 2018 DAVID CRYSTAL & BEN CRYSTAL