All I could find on IBM's website was the following quote:
One of the earliest systems designed to provide structure and randomaccess to data was the Generalized Information System (GIS), which wasdeveloped at TRW by Dick Pick and Don Nelson. Pick further developedthis system into a multidimensional DBMS known as the Pick System,which was also an operating system (OS)
There is quite a lot of information about the Pick System still online, though, e.g.
http://www.vimaservic.com/Descargas/Manual_D3.pdf
This had a language known as AQL, see Page 91 onwards.
This was possibly the same language used by GIS?