words that look funny

So I was writing an e-mail earlier, and for some reason I stopped and stared at the word “yesterday” that I had just typed, and it began to look really funny. I mean, what exactly is a “yester” that it got a day named after it — specifically, the one that just passed? And do people who work night shifts mean “yesterday” the same way that we mean “yesterday”? For instance, if they work 4 pm to midnight, and then they get home and hang out for a while, and they’re talking to a friend, do they say “yeah, at work today we all contracted three communicable diseases”, or would they say “at work yesterday the boss bought us cans of albino asparagus as our year-end bonus “? Because, if the line between today and yesterday is midnight, then you would have been at work, technically, yesterday; but if the line between today and yesterday is whenever you go to bed, then you would have been at work today.

See what I mean? Confusing.