Does anyone know why sometimes its refered to as 110 and oters it's 120, and so on. I understand that according to the NEC we use 120. But what is the history of 110, 115, 120, or 130?

You have nominal voltages and you have connected system voltages. The real tested voltage is the connected voltage which can vary as great as 10V + or - from the nominal or "named" voltage. See the two Article 100 definitions. The NEC also identifies the nominal voltages in section 220.2(A). And if you look at the notes to Tables 430.148 - 430.150 (2002 NEC), you will see a system voltage range for each rated motor type.

It appears Edison was the first to establish a standard voltage distribution system. One theory is that 120V was used due to the fact that telegraphs required at 60V at each end or station resulting in a 120V potential. Edison was a major player of the telegraph industry. Another theory is that when Edison was trying to perfect the incandescent lamp, he was trying to accurately imitate the lighting provided by a standard gas lamp of the day. Once he established a fixed resistance filament, he simply raised the voltage until the intensity of the lamp matched that of a gas lamp. The resulting voltage was around 110 Volts.

The earlier codes and electrical books reference 110/220 nominal voltages. At some point 115 volts was even referenced. Today of course is 120V and appears to be regular adjustments in terminology as electrical systems become more efficient, standardized, and free of voltage drops.

Some equipment today such as lamps and hair dryers give higher nominal voltage ratings to give the appearance of higher power (P=ExI). So it may be possible the super deluxe hair dryer can produce 1950 Watts of blow drying power but only if the connected voltage is 125V. Same thing with lamp wattages.

I agree with Bryan. Well said!

I actually was testing hair dryers for a while with my Fluke clamp on. Even with my normal 123-124v at the plug I never found one that really used more than 12 amps. I think the hair dryer ratings are like air compressor ratings (6.5HP with a NEMA 5-15 plug).

I did do a little googling on the original question and it appears Edison originally used 110VDC and that gradually got ramped up to 120v to get more bang for the wiring buck. I couldn't really find a good story though.

Also, keep in mind that voltages are sinusoidal and the actual voltage varies per time. This is why RMS voltages are used. Take a look at this article which gives a pretty good explanation http://www.ee.unb.ca/tervo/ee2791/vrms.htm Vrms = Vpeak * 0.707.

Exception:
Some loads are nonlinear (nonsinusoidal) due to harmonic distortion. These are voltages and currents that do not conform to a linear or sinusoidal waveform.