1
general::
Wander off the right path or subject; also, wander into evil or error. For example, It was hard to follow the lecturer's gist, since he kept going astray, or The gang members led him astray, and he ended up in court. This expression alludes to sheep or other animals that stray from the rest of the flock. Indeed, Handel's oratorio Messiah (1741) has this chorus: "All we like sheep have gone astray, Every one to his own way." [c. 1300]
American Heritage Idioms