Rhadamanthus (n.)

name of one of the three judges of the Underworld in Greek mythology, son of Zeus and Europa, from Latinized form of Greek Rhadamanthos, whose name seems to contain Greek rhadamos "branch, twig, shoot." Used in English from 1580s allusively of inflexible judges or solid and final judgment. Related: Rhadamantine; Rhadamanthean.