slate [ME] This is from the Old French esclat ‘a piece broken off’. Slat [LME] is a variant which meant ‘roofing slate’ until it developed the current sense in the mid 18th century. The related French esclice ‘splinter’ gives us slice [ME] and their common Germanic source also gives us slit [OE]. Shops and bars used to use writing slates for keeping a record of what a customer owed. This is the origin of the expression on the slate, ‘to be paid for later, on credit’. In the sense ‘to criticize’, dating from the mid 19th century, slate and may be related to a Scots use of slate meaning ‘to set a dog on’, which is from Old Norse.