Someone who knows their way around a car is certainly familiar with SAE or Society of Automotive Engineers. SAE tools are the ones that are measured in fractions of inches. SAE will also be found on oil and horsepower ratings.
Yes AC/DC is one of the greatest rock bands to ever play but it also stands for alternating current and direct current. Alternating current changes direction periodically while direct current moves in a straight line. Most electronics use direct current. AC delivers power to houses and office buildings because it travels over distances better.
NPT or National Pipe Thread, is a U.S. standard for tapered threads on threaded pipes and fittings. NPT goes back to 1864 when William Sellers created a standard for nuts, bolts and screws.