That sounds like the state historian's handiwork. "Friendship" appears to have always been a popular place name in Maryland. And there appear to be similarly named unincorporated villages wherever there was a Quaker meeting house. For instance, I just pulled my MDOT: State Highway Administration road map off the shelf and found two different "Friendship" place names (in Anne Arundel County east of Chesapeake Beach and in Montgomery County north of Damascus), "Friendship Heights" (incorporated, south of Bethesda), and "West Friendship" (west of Ellicott City). Thus, Baltimore's airport could have been located anywhere in the state and still held the same place name marker.
[Edited 2004-03-24 07:52:58]