The Volokh Conspiracy - Hidden Connections:

What do these words have in common? You'll know it when you have it. Once you get it, post some more examples in the comments (with citations, please).

Water
Nanny
File
Travel

UPDATE:

I've posted the following challenge in the comments: When did the phenomenon that joins the four words above begin? What is the earliest reference to an example of it that we can find?

	[Puzzleblogger Kevan Choset, August 5, 2005 at 11:25am] Trackbacks Hidden Connections: What do these words have in common? You'll know it when you have it. Once you get it, post some more examples in the comments (with citations, please). Water Nanny File Travel UPDATE: I've posted the following challenge in the comments: When did the phenomenon that joins the four words above begin? What is the earliest reference to an example of it that we can find?