Schedule. It's something we use every day. A time table we keep. An action we perform daily for things like, oh, blog posts. ;-) As both a verb and a noun, it's a word in such common use that I was shocked to discover it didn't take on that oh-so-known meaning until railroading days! That's right, the verb came into being in 1862, and the noun in 1863, both in conjunction with railroads scheduling their trains.
What was it before then, then? Well, originally it meant "a slip of paper with writing upon it." In that sense it's been around since the 14th century, taken from a Greek word. These slips of paper were often attached to a document as an appendix--think of those schedules you have to attach to your tax form (ugh, that time of year again!) and it clicks into place.
It's a fairly easy jump then to these slips of paper with writing on them that the railroads would use, but I gotta say--I'm still surprised at how long it took and how completely the word has taken on this "new" meaning, and whenever I run into a place in a historical novel where I want to use "schedule," I'm at a complete loss. One time in particular I remember floundering a good while before I decided the character should just keep a calendar rather than a schedule, LOL, and that she would just have to pencil an event onto it rather than schedule it. ;-)
I hope everyone had a lovely, green St. Patrick's Day and is set for a great week! Here in Maryland we're really enjoying the early arrival of spring. =)