[flashback to Marshall arriving at the apartment as Ted stacks books on a shelf:]
Marshall: Hey. What's that?
Ted: A 1986 World Book encyclopaedia. [en-sahy-kluh-pay-dee-uh] It's exactly the one I grew up with.
Marshall: Encyclopaedia?
Ted: Oh, you think it should be pronounced encyclo-pee-dia. It's a common mistake. But if you look at that squished together "ae" symbol in this here encyclopaedia, you'll learn that it's a ligature derived from the Anglo-Saxon rune...
[The bookshelves collapse, ripping off a portion of plasterboard and exposing the building's red brick walls]
Marshall: You know, you're gonna have to paedia for that.