late 14c., from Latin separatus, past participle of separare "to pull apart," from se- "apart" (see secret (n.)) + parare "make ready, prepare" (from PIE root *pere- (1) "to produce, procure"). Sever (q.v.) is a doublet, via French. Related: Separated; separating.
"one of the individual parts of a corolla of a flower," 1726 (earlier petala, 1704), from Modern Latin petalum "petal" (17c.), from Greek petalon "a leaf; leaf of metal, thin plate," noun use of neuter of adjective petalos "outspread, broad, flat," from PIE root *pete- "to spread." Related: Petaline.
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Harper, D. (n.d.). Etymology of sepal. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/sepal