Some Shimano front derailleurs are held together with bolts that can loosen, leading to erratic front derailleur action, high-siding the chain and eventually falling apart. They had no name until recently. I had not seen a derailleur with Marvin Bolts in a while, so when a customer named Marvin brought a bike in with front derailleur problems, I took care of one of the issues, but forgot the Marvin Bolts. One fell out, and I ended up buying Mr. Marvin a derailleur before never seeing him again because I am obviously a negligent, untrustworthy bastard. Gone he may be, but he has given his name, as Ned Overend did to the Ned Gear and Tinker Juarez did to the Tinker Bolt.
The Tinker Bolt dates from the 1990s, when Mr. Juarez supposedly lost the bolt that holds the back of the the front derailleur cage together during a race. Legend has it he was unable to shift to the big ring, thus losing that race.
Check your bike for Marvin Bolts. Tighten them with your 3 mm hex key.