From The Free Dictionary:
A rope, chain, or similar restraint for holding an animal in place, allowing a short radius in which it can move about.
A similar ropelike restraint used as a safety measure, especially for young children and astronauts.
Nope - I'm not a young child, nor an astronaut. Maybe I wanted to be an astronaut when I was a young child, but that doesn't count.
The extent or limit of one's resources, abilities, or endurance: drought-stricken farmers at the end of their tether.
I might be at the end of my tether. But only because I'm tethered when I want to be untethered.
When we first connected two computers together to form a network, we created a connection, or a tether, that mechanically bound the computers to each other. That binding lasted until early wireless technology permitted a computer to be on a network without being wired to that network. Now we freely roam about on wireless networks, untethered. Sort of. We still have to be near a wireless network access point, but that's not to hard do do now days.
So we are untethered, right? Not quite -we still need our power cords, wall warts, power bricks and international adapter plugs. But to be tethered to a wall only by power requirements is a huge advancement the overall state of personal freedom. We can go for a couple hours at time freely moving about the home, workplace or nerd conference, and enjoy the ability to move about unhindered by a 'rope, chain or similar restraint'.
Until the energy runs out. Then we frantically re-attach ourselves to our tethers, this time the -/+ 12vdc ones. And as the day goes on, and we burn our battery reserves, we find ourselves budgeting our wall-connect time, scrambling for conference tables near the wall jack, pulling extension cords out of oversized briefcases (or undersized steamer trunks on wheels) in a desperate attempt to stay attached to the wireless network until the last BOF of the day. Yep - we frantically scramble to wire ourselves to a wall so that we can stay connected to a wireless network.
Of course as the day goes on, we find that the ratio wall-tethered to untethered time isn't quite enough to keep us alive all day, and we inevitably enter the downhill spiral of ever shorter periods of untethered freedom followed by ever longer attachments to wall plugs, until we finally can leave our leash and our oversized briefcases (or undersized steamer trunks on wheels) in the hotel room and enjoy the conference.
Somewhere along the line we've decided to trade power or performance for battery life, almost as though we are afraid to be untethered for more than 2 or 4 hours. The thought of being completely disconnected, free to move more that 3 meters from a wall for more than 2 hours, must scare us. Or else we'd have figured out a solution by now.
There simply are no contemporary laptop computers that have reasonable battery life, where reasonable is defined as somewhere close to a normal day. The best we've come up with is 2 hours of freedom for $1000, or 4 hours of freedom for $2000. Or in the case of my home notebook, one hour of freedom for $500.