periscope (n.)

word-forming element in words of Greek origin or formation meaning "around, about, enclosing," from Greek peri (prep.) "around, about, beyond," cognate with Sanskrit pari "around, about, through," Latin per, from PIE root *per- (1) "forward," hence "in front of, before, first, chief, toward, near, around, against." Equivalent in sense to Latin circum-.

word-forming element indicating "an instrument for seeing," from Late Latin -scopium, from Greek -skopion, from skopein "to look at, examine" (from PIE root *spek- "to observe").