Hardly; barely; only just; used to indicate that something is almost not the case or almost did not happen.
From 'scarce' plus '-ly', where 'scarce' comes from Old French 'escars' meaning 'restricted, insufficient'. This traces back to Vulgar Latin 'excarpsus', from Latin 'excerpere' meaning 'to pick out, extract', suggesting something that has been picked over and reduced.
The etymology of 'scarcely' reveals an interesting metaphor - when something is scarce, it's as if it has been 'picked over' until almost nothing remains. This harvesting imagery makes 'scarcely' particularly powerful for describing situations where resources, time, or opportunities have been nearly exhausted.
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