American colloquialism meaning, roughly, "since long ago." The etymology is fuzzy (Bartlett's 15th edition lists it as anonymous) but it seems more likely than not that the Hector in question is the Trojan hero. Several tedious usenet discussions have failed to resolve the issue.
Usage: "I haven't been to Fort Worth since Hector was a pup."
Similar phrases include "since Adam was a boy". | 
