Properly the granum (granary) or farm of a monastery, where the corn was kept in store. In Lincolnshire and other northern counties any lone farm is so called.
Houses attached to monasteries where rent was paid in grain were also called granges.
Till thou return, the Court I will exchange For some poor cottage, or some country grange.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894