This work is centered on the role of the Basque language as an immediate factor on the origin of Castilian suffixation in -VrrV. It is therefore a research dealing with the contacts between the Basque and Castilian languages. It promotes a perspective anchored in the conviction that both philologies neither have ever existed nor will exist isolated. If they yielded to temptations to assume their isolation and ignore their linguistic vicinity, then the philologies of both languages would risk and hold to extremes of deficiency and doctrinal impoverishment.