in botany, "leaf of the calyx," 1821, from French sépal, from Modern Latin sepalum (H.J. de Necker, 1790), coined from Latin separatus "separate, distinct" (see separate (v.)) + petalum "petal" (see petal).
early 15c., separaten, transitive, "remove, detach completely; divide (something), sever the connection or association of," 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. Intransitive sense of "to part, be or become disunited or disconnected" is by 1630s of things, 1680s of persons. 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.
<a href="https://www.etymonline.com/word/sepal">Etymology of sepal by etymonline</a>
Harper, D. (n.d.). Etymology of sepal. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/sepal