Jolteon

Jolteon (サンダース, Sandāsu, Thunders in original Japanese language versions) is one of the evolutions of Eevee that is caused by radiation from a thunderstone. Jolteon is covered with spikey, bright yellow fur, with white spiky fur surrounding its neck. Its fur sparks with electricity constantly; it can be soft to the touch or turn into sharp needles that can be fired when it is angered. Jolteon is able to gather negative ions from the atmosphere, using the resulting electricity to create lightning bolts of up to 10,000 volts. Its individual cells also create small electrical charges on their own, which combined with the static electricity caused by its body can result in powerful electric-type attacks. It's very sensitive which causes it to constantly charge as it quickly changes moods. It can also make lightning and cause small thunderstorms. In Pokemon XD: Gale of Darkness, as well as other pokemon games of the third generation and on(when pokemon abilities were introduced), Jolteon is said to be able to absorb electric attacks and turn it into HP (in other words it heals when hit with electric moves). The ability is called Volt Absorb.

Name Origin
Jolteon's name originates from Jolt and Eon. Jolt is the action of sudden jerks. In this case, it means to electrify another. Eon is just an extension meaning a long period of time, making sense because Jolteon is one of the seven evolutions of Eevee.