shale

Etymology

From Middle English schale (“shell, husk; scale”), from Old English sċealu (“shell, husk, pod”), from Proto-Germanic *skalō (compare West Frisian skaal (“dish”), Dutch schaal (“shell”), schalie (“shale”), German Schale (“husk, pod”)), from Proto-Indo-European *(s)kelH- (“to split, cut”) (compare Lithuanian skalà (“splinter”), Old Church Slavonic скала (skala, “rock, stone”), Polish skała (“rock”), Albanian halë (“fish bone, splinter”), Sanskrit कल (kalá, “small part”)), from to split, cleave (compare Hittite [script needed] (iškalla, “to tear apart, slit open”), Lithuanian skélti (“to split”), Ancient Greek σκάλλω (skállō, “to hoe, harrow”)). Doublet of scale. See also shell.

noun

1. A shell or husk; a cod or pod.
   the green shales of a bean
2. (geology) A fine-grained sedimentary rock of a thin, laminated, and often friable, structure.
   As on all large green roofs, the soil is not dirt exactly but a gravel-like growing medium of granulated pumice, shales, clays and other minerals. March 23, 2007, Patricia Leigh Brown, “The Window Box Gets Some Tough Competition”, in New York Times

verb

1. To take off the shell or coat of.