To overflow the banks or boundaries; to exceed or surpass limits; to sally forth or burst out.
From French 'déborder' meaning to overflow, derived from 'de-' (out) and 'bord' (edge, border). The term originally referred to water overflowing riverbanks but expanded to mean any overflowing or exceeding of limits.
The same 'bord' that gave us 'debord' also gave us 'border,' 'aboard,' and 'boatswain'—it's a word about edges that comes from the Germanic root for a flat surface, and seeing how many words cluster around it shows how much we think about boundaries.
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