"instrument for visually recording an electrical wave," by 1907, a hybrid formed from Latin oscillare "to swing" (see oscillation) + -scope. In reference to the modern cathode-ray oscilloscope, by 1927.
"kind of vibration in which a body swings backward and forward," 1650s, from French oscillation and directly from Latin oscillationem (nominative oscillatio), noun of action from past-participle stem of oscillare "to swing," from oscillum "a swing," which usually is identified with the oscillum that meant "little face" (literally "little mouth"), a mask of open-mouthed Bacchus hung up in vineyards as a charm (the sense evolution would be via the notion of "swinging in the breeze"); from PIE *os- "mouth" (see oral). Figurative use, in reference to a swinging back and forth (in opinion, attitude, etc.) is by 1798.
[instrument for viewing] 1872, shortened from telescope, microscope, etc., in which the element (Latinized) is from Greek skopein "to look" (from PIE root *spek- "to observe"). Earlier used as a shortening of horoscope (c. 1600). Extended to radar screens, etc., by 1945 as a shortening of oscilloscope.
<a href="https://www.etymonline.com/word/oscilloscope">Etymology of oscilloscope by etymonline</a>
Harper, D. (n.d.). Etymology of oscilloscope. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/oscilloscope