To release or free from a cage or confinement.
From 'dis-' (to reverse) plus 'cage,' from Old French 'cage.' This word parallels how 'dis-' attaches to container words to mean removal.
Notice how 'discage,' 'disbutton,' and 'disbutton' all follow the same pattern—early English had amazing freedom to create new verbs this way, but most died out as certain prefixes became unfashionable.
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