Definition of "unco"

It was noted by them that kenned best that her cantrips were at their worst when the tides in the Sker Bay ebbed between the hours of twelve and one. At this season of the night the tides of mortality run lowest, and when the outgoing of these unco waters fell in with the setting of the current of life, then indeed was the hour for unholy revels.

1902, John Buchan, The Outgoing of the Tide

And the second quean was Hope and she was near as unco as Faith, but had right bonny hair, red hair, though maybe you'd call it auburn […] .

1932, Lewis Grassic Gibbon, Sunset Song (A Scots Quair), Polygon, published 2006, page 18

‘Ye should tear up this carpet, Robbie,’ Uncle Peter called back over his shoulder. ‘It's most unco wearisome when a body′s leg-weary.’

1920, Tod Robbins, “Who Wants a Green Bottle?”, in Freaks And Fantasies, published 2007, page 70

Jamie has met only two kids of women: the mainly elderly and unco good who belong to his father's congregation, and those who drink in pubs and shebeens used by nearly penniless medical students.

1996, Alasdair Gray, “The Story of a Recluse”, in Every Short Story 1951-2012, Canongate, published 2012, page 267

‘Aren′t he the most unco kid you ever come across?’ Norm refused to have Kevin on his boat even if he begged to be taken because he was too clumsy.

2006, Alexis Wright, Carpentaria, page 106