Scottish National Dictionary (1700–)
HORSO, n.1 A sizeable horse, a big horse, in contradistinction to horsie, the diminutive. Cf. Manno.
ne.Sc. 1792 Trans. Soc. Antiq. Scot. 418:
It is not many years ago, since I heard a farmer's wife laughing heartily at her neighbour, for calling a horse of middle size a horsie! “He is more like a horso” said she.
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"Horso n.1". Dictionary of the Scots Language. 2004. Scottish Language Dictionaries Ltd. Accessed 18 Feb 2019 <http://www.dsl.ac.uk/entry/snd/horso_n1>
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