Re: Brainstorming
From Wiki of Ice and Fire: The custom of fosterage is common among the nobility of Westeros. It is seen as a way of establishing friendships and alliances.[1] For example, Lord Jon Arryn became a second father to his two foster children, Eddard Stark and Robert Baratheon, during the years they were fostered by Arryn at the Eyrie.[2] Additionally, fosterage is seen as a means of education.[1] For example, boys can be fostered out as squires, training for knighthood.[3] Most commonly the fostered child is male,[1] although it is not unheard of for females to be fostered. The fostered child can be trueborn or bastard born.[4] Hostages may be fostered; for example, Theon Greyjoy.[5] In the Free City of Norvos, children are usually not fostered out.[6][7]
So yes, terms are somewhat interchangeable.