Years ago, I had four sites in the same niche with similar content. 9 months ago, I shutdown three of the websites and parked the domains, leaving me with just one website in this niche.

Some of the content from the shutdown websites was good and I would like to republish it on my one remaining website. Is it "safe" to re-use the content from the shutdown websites and republish it on the one remaining site? Or does Google remember that it once lived on a different domain and therefor it's duplicate content (even though the original no longer exists)? Anyone have experience with this?