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-.
"act of walking about," 1570s, from Latin ambulationem (nominative ambulatio), noun of action from past-participle stem of ambulare "to walk, go about" (see amble (v.)). The word was used earlier in reference to the spread of disease (1540s).