Definition of "coost"

I had but little butter, an' that I coost on the coals.

1868, Alexander Hislop, The Proverbs of Scotland‎

1783 Death And Dying Words Of Poor Mailie, The Author's Only Pet Yowe., An Unco Mournfu' Tale As Mailie, an' her lambs thegither, Was ae day nibbling on the tether, Upon her cloot she coost a hitch, An' owre she warsl'd in the ditch: There, groaning, dying, she did lie, When Hughoc he cam doytin by.

1780, Robert Burns, Poems And Songs Of Robert Burns‎