To drip or let liquid fall in drops; to trickle (Scottish and dialect).
From Middle English or Old English 'dreopan' (to drop/drip), related to 'drip'. The word preserved in Scottish dialect shows how regional speech conserves ancient vocabulary.
It's fascinating that 'dreep' and 'drip' are actually related—they're both attempts to spell the onomatopoeia of water falling, preserved in different English dialects and time periods.
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