Frame of Mind
Disposition. A printer's frame is a stand on which the type is disposed; a founder's frame is a mould into which molten metal is disposed or poured; a weaver's frame is a loom where the silk or thread is disposed or stretched for quilting, etc.; a picture frame is an ornamental edging within which the picture is disposed; a mental frame, therefore, is the boundary within which the feelings of the mind are disposed.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894