A backyard was an area behind one's house that was used for recreational purposes. The term could also be used as a metaphor for one's immediate territory. (DS9: "In the Pale Moonlight", VOY: "Resolutions")
In 1996, a man who was taping a backyard barbecue with a camcorder caught an image of a time traveling USS Voyager. (VOY: "Future's End")
Jonathan Archer used to chase Danica Erickson around the backyard with a plastic laser pistol, a fact he used to underscore the difficulty he imagined she'd have taking advice from him. (ENT: "Daedalus")
In the first draft script of ENT: "Fusion" (which had the working title "Equilibrium"), Jonathan Archer mentioned having had a "backyard telescope" in his youth.