1) The solid substance left after mineral coal has been deprived of its volatile constituents.
The modern usage is said to date from the seventeenth century with the earliest examples in south Yorkshire. A lease of Sheffield Park colliery in 1737 used both the verb and the plural noun: it granted John Bowden the right to coake or make and convert into coakes any of the coal that was mined there. One possible earlier reference has been noted: c.1560 his colks to ryddell and clene to swepe, Woodsome. It may share the same derivation as the dialect word ‘colk’ or ‘coke’ which refers to the core of an apple and is on record from the 1300s.