Automatic Oil Cup
Even if you've never heard of the automatic oil cup, you've probably uttered the phrase that entered the lexicon because of it. The automatic oil cup was the invention of Elijah McCoy, who was born in 1843 to parents who had escaped slavery via the Underground Railroad. McCoy was sent to Scotland for school, and he returned as a "master mechanic and engineer" [source: MIT]. However, the job opportunities for a black man -- no matter how educated -- were limited. The only work McCoy could find was with the Michigan Central Railroad.
McCoy's job was to walk along the trains that pulled into the station, oiling the moving parts by hand. McCoy realized that a person wasn't necessary for this job, and he invented the automatic oil cup, which would lubricate the train's axels and bearings while the train was in motion. As a result, trains didn't have to stop as frequently, which cut down on costs, saved time and improved safety. The oil cup was a huge success, and imitators began producing knockoffs. However, savvy engineers knew that McCoy's cup was the best, so when purchasing the part, they'd ask for "the real McCoy."