This is an expression which means "use your own product", or "take your own advice".
I used to do general-purpose stuff (web browsing, email etc) with a Windows 98 computer. Then it got hit - I'd just visited The Register (a tech news web site) and one of the advertisements there did a drive-by install on my system. That means, it just did it, it didn't ask me to click on anything. Just the act of visiting the site, installed the malware.
I spent half an hour trying to get rid of it; it kept coming back, Then I saw sense, and decided to just do a clean install. So I zapped the hard drive (wrote zeroes all over it), and I was just about to re-install Windows 98, when I thought, hang on. I'll go Linux.
Ever since then (and that's several years ago), it've been using Linux on my general purposes workstation; for web browsing, email, logging in to other computers, and so on.
I get hundreds of emails enclosing malware each week. Hundreds! I just delete them unread, unopened. Not a problem. But it makes you think. And when Ian (Kewfriend) reported what happened to him (see previous blog), I advised people to get a cheap, second-hand laptop and use that for anything financial, such as buying things online, using Ebay, Paypal and any bank stuff. And don't use it for installing software, general-purpose web surfing, email, or anything else apart from the stuff that you hope to keep secure. Money stuff.
I've always felt that just using Linux is sufficient protection for me. But I thought that several years ago, and the situation has clearly gotten a lot worse.
So I dug out a laptop that had a couple of missing keytops, plugged a keyboard and mouse (I don't like trackpads) into it, and I'm installing Linux on it. It's not a great laptop; I inherited it from daughter.2 because of A) the missing keycaps and B) a loose power connector. And it's not fast. But it's good enough for using as my secure computer.
Because I'm planning to eat my own dog food.