1660s, from Greek baros "weight" (from suffixed form of PIE root *gwere- (1) "heavy") + -meter. The name probably was coined (and certainly popularized) by English scientist Robert Boyle (1627-1691). The instrument was invented 1643 by Italian physicist Evangelista Torricelli and was at first known as the Torricelli tube.
also sea-coal, old name for "mineral coal, fossil coal" (as opposed to charcoal), late 13c., secol; earlier, in Old English, it meant "jet," which chiefly was found washed ashore by the sea. See sea + coal (n.). The coal perhaps was so called for its resemblance to jet, or because it was first dug from beds exposed by wave erosion. As it became the predominant type used, the prefix was dropped.
metallic element, first isolated in pure form in 1875, named for ceria, the name of the earth from which it was taken, which was discovered in 1803 and named by Berzelius and Hissinger for Ceres, the minor planet, "whose discovery (in 1801) was then one of the most striking facts in physical science" [OED]. The planet was named for the Roman goddess Ceres, from a root meaning "to grow." With metallic element ending -ium. Related: Ceric.
"broom-shaped," by 1891, from Latin scopa "broom" (see scopa) + -arious. Late Latin scoparius was "a sweeper." An older English word in the same sense was scopiform (1794).