late 14c., "move upward," from Latin ascendere "to climb up, mount," of planets, constellations, "come over the horizon," figuratively "to rise, reach," from ad "to" (see ad-) + scandere "to climb" (see scan (v.)). Also in 15c. used with a sense "to mount (a female) for copulation." Meaning "slope upward" is from 1832. Related: Ascended; ascending. An Old English word for it was stigan.
<a href="https://www.etymonline.com/word/ascender">Etymology of ascender by etymonline</a>
Harper, D. (n.d.). Etymology of ascender. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/ascender