In Reply to: Plugging along posted by Glo_wing on January 02, 2010 at 21:50:
: Where does the phrase "plugging along" come from?
The Oxford English Dictionary includes the use that you refer to: (s.v. plug, v.) "5. intr. To work steadily away at something; to persevere doggedly; to plod, to move steadily. Freq. with away, along, etc."
The OED gives examples from 1867 forward, but only in 1900 goes it find an example exactly like what you have in mind. I don't see the connection with plugging something up or putting a plug in something. There might be a connection with old, worn-out horses that are sometimes called plugs, but which way the connection goes I know not.