Meaning

noun (formerly) a writing tablet made of slate

noun thin layers of rock used for roofing

noun a fine-grained metamorphic rock that can be split into thin layers

originThe noun is derived from Middle English sclate, slat, slate (“type of rock; roofing slate; writing slate”), from Old French esclate, a feminine form of esclat (“broken piece, shard”) (modern French éclat), from Old French esclater (“to break, shatter”), from Frankish *slaitijan (“to split, break”), from Proto-Germanic *slaitijaną, the causative of *slītaną (“to cut up, split”); further etymology…

Etymology from Wiktionary, CC BY-SA 3.0