Those are just words that tend to get redefined. When they first started
keeping track of economic events, a sever down turn was called a
"panic". That was because people panicked and ran to the banks to get
their money out. The panic of 1873 was the worst so to make people feel
better, they no longer used the word panic to describe a severe economic
downturn, they used a less threatening word "Depression." Well, along
comes the severe economic down turn of the late 20s lasting into the
30s. After it was over the economists decided that depression was too
harsh a word so they started calling them recessions.