1640s, from Italian telescopio (Galileo, 1611), and Modern Latin telescopium (Kepler, 1613), both from Greek teleskopos "far-seeing," from tele- "far" (from PIE root *kwel- (2) "far" in space or time) + -skopos "watcher" (from PIE root *spek- "to observe"). Said to have been coined by Prince Cesi, founder and head of the Roman Academy of the Lincei (Galileo was a member). Used in English in Latin form from 1619.
"to force together one inside the other" (like the sliding tubes of some telescopes), 1867, from telescope (n.). Related: Telescoped; telescoping.