The Collaborative International Dictionary of English v.0.48:
Adrogation \Ad`ro*ga"tion\, n. [L. adrogatio, arrogatio, fr. adrogare. See Arrogate.] (Rom. Law) A kind of adoption in ancient Rome. See Arrogation. [1913 Webster]Bouvier's Law Dictionary, Revised 6th Ed (1856):
ADROGATION, civil law. The adoption of one who was impubes, that is, if a male, under fourteen years of age; if a female, under twelve. Dig. 1, 7, 17, 1.