Naming new car models is always tough. The latest head-scratcher is GM's decision to rebrand the replacement for its Aveo subcompact as the 2012 Chevrolet Sonic, a name better associated in the U.S. with hedgehogs or hamburgers.

But that's nothing compared to the challenge of naming electric-car brands and models.

Have all the good names now been snapped up? Not quite ... but let's look at what's already been claimed.

opel ampera geneva live 003

opel ampera geneva live 003

2011 Chevrolet Volt and Opel/Vauxhall Ampera

"Volt" may be the single most familiar electrical unit to most consumers, so the unit of electrical power named after Italian physicist and battery inventor Alessandro Volta was a smart and logical choice for the 2007 Detroit Auto Show series hybrid concept car that wowed the industry. It launched in the U.S. this month.

The European version is called the Ampera, a takeoff on Ampere, the unit of electrical current named after André-Marie Ampère, the French mathematician and physicist often deemed the father of electrodynamics. (There's also converter AMP Electric Vehicles.)

2011 Nissan Leaf

2011 Nissan Leaf

2011 Nissan Leaf

For its first production battery electric vehicle (and winner of GreenCarReports' 2011 Best Car To Buy award), Nissan avoided electrical terms altogether and opted to stress the green aspect. "Leaf" is short, neutral, and nicely evocative of a calm, quiet forest--one unblemished by the vehicular emissions that the Leaf doesn't produce.

Tesla Model S Sedan

Tesla Model S Sedan

2011 Tesla Roadster

Silicon Valley startup Tesla Motors got in early, naming itself after famed electrical engineer Nikola Tesla. Its first vehicle, the Roadster, is simply named for its body style. Tesla's next car, the yet-to-be-launched Model S luxury sports sedan, follows the alphanumeric tradition of German makers like Mercedes-Benz (E-Class), BMW (5-Series), and Audi (A6).

2011 Coda Sedan

Southern California startup Coda Automotive wanted its name to convey "something that's separate, complete by itself, and independent, said now-departed CEO Kevin Czinger. "The notion is that it completes and perfects something that came before it ... the gasoline-engined car."

Like Tesla, its model name is a body type: the Sedan. (The 2011 Coda Sedan will be delayed until the middle of next year.)

Fisker logo

Fisker logo

2011 Fisker Karma

The sleek, range-extended luxury sports sedan launched by this startup car company is named after its founder, stylist Henrik Fisker. At least its model name, Karma, coneys a soothing, Zen-like image of harmony and oneness with nature befitting its ability to run up to 50 miles on electricity alone.

While Fisker showed what it called the first production Karma at the Paris Motor Show, and first cars are to arrive at U.S. dealers in March or April, concern over the company's future has grown louder.

But what's left?

Other terms and units already have automotive applications. "Coulomb" is the name of a startup that provides plug-in vehicle charging stations: Coulomb Technologies. "Joule" is used for a unique silvery-green color offered on the Chevy Volt: Viridian Joule.

2011 Chevrolet Volt

2011 Chevrolet Volt

That leaves a long list, compiled almost two years ago by British magazine Autocar. Among candidates that haven't yet been snapped up (or at least aren't yet publicly announced) are Farad, Henry, Kelvin, Newton, Ohm, Pascal, Siemens, Watt, and Weber.

Some of them are, ummm, dubious. A model called the "Watt" would be the butt of "What?" jokes. (General Electric has also heavily advertised its WattStation electric-car charger.)

The "Newton" might bring to mind Apple's pioneering but flawed Newton personal digital assistant. "Weber," the unit of magnetic flux, may remind old-car fans of carburetors, and is likely still a brand name of its own.

But we think Fisker could follow the Karma with the "Ohm," to play up its Zen mantra aspect. And Farad (capacitor charge), Kelvin (temperature scale), and Pascal (pressure) may be up for grabs.

We just hope and pray no maker is foolish enough to adopt "Siemens" (the unit of electrical conductance and admittance) as a model name. Because it'll be all over the first time some eager engineer says to a ranking executive, "Hey, c'mon down to the studio--you've got to look at our new Siemens!"

logos for AMP Electric Vehicles and Remy, used on Amp'd Equinox electric conversion

logos for AMP Electric Vehicles and Remy, used on Amp'd Equinox electric conversion

[Autocar]