1540s, "shaped like or resembling an arrow or arrowhead," as if from Latin *sagittalis, from sagitta "arrow" (see Sagittarius).
Entries linking to sagittal
Sagittarius n.
southern constellation; ninth sign of the zodiac, late Old English, from Latin, literally "archer," properly "pertaining to arrows," from sagitta "arrow," which probably is from a pre-Latin Mediterranean language.
Meaning "person born under Sagittarius" is attested from 1940 (properly Sagittarian, which is attested by 1911). The star-picture represents a centaur drawing a bow, scholars suspect it to have been originally a Babylonian god, but to modern observers it only looks vaguely like a teapot.