c.1300, aphetic of O.Fr.
estraier "wander about," lit. "go about the streets," from
estree "route, highway," from L.L.
via strata "paved road" (see
street). On another theory, the O.Fr. is from V.L.
*estragare, a contraction of
*estravagare, representing L.
extra vagari "to wander outside" (see
extravagant). Fig. sense of "to wander from the path of rectitude" is attested from c.1325. The noun meaning "domestic animal found wandering" is earlier (1228), from O.Fr.
estraié "strayed," pp. of
estraier. The adj. is first recorded 1607.