Deposited money in a bank, or tilted to the side (as an airplane or race car turning), or formed into a ridge or embankment.
From Middle English 'bank' (ridge of earth), later extended to mean the side of a river, then metaphorically to financial institutions and tilting motions.
When you 'bank on something,' you're tilting your hopes toward it like a plane banking in a turn! The financial meaning came because banks were built on the banks of rivers.
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