Or from Latin baculum a stick, because the squire would practice with a staff, not a sword. Meaning evolved from knight in training to young unmarried man (early 14c.). Bachelor party as a pre-wedding ritual is from 1882.
A transcutaneous electrical nerve stimulation (TENS) unit is a device that sends small electrical currents to targeted body parts. These currents are used to relieve pain. Some TENS units are designed for use in a hospital or healthcare facility.
For some people, a transcutaneous electrical nerve stimulation (TENS) machine is used as an alternative to painkilling medication. A TENS machine is a small portable, battery-operated device which is worn on the body. The box is attached by wires to sticky pads stuck to the skin.