Scottish National Dictionary (1700–)
BROONIE, n.2 “Liquid or ‘wort' drawn off malt in brewing. Prob. a good deal of superstition lingered about the word; to have spoken of ‘water' might have ruined the ale” (Ork. 1929 Marw.).[O.N. brunnr, a spring or well (Zoëga), O.E. burna, brunna, a stream or brook (Sweet), Norw. brunn, a water pit (Torp), Ger. brunnen, spring, well. Cf. Brin, n.1, brinny water (s.v.), and Burn, n., 2, water used in brewing, then the brew itself.]
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"Broonie n.2". Dictionary of the Scots Language. 2004. Scottish Language Dictionaries Ltd. Accessed 22 Jun 2018 <http://www.dsl.ac.uk/entry/snd/broonie_n2>
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