(Can we find and add a quotation of Chaucer to this entry?)
References
overslop in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913
Etymology
From Middle Englishoversloppe, Old Englishoferslop, oferslype(“an overgarment; surplice”), equivalent to over- +slip. Cognate with Icelandic yfirsloppur(“overalls”).