Red, wasn't one of the more ominous of the early iterations of 'decimate' the use of a Roman army form of punishment for extreme cowardice/dereliction of duty? As I recall, the offending legion/century/whatever the number (they were on the metric system, LOL), was lined up in formation, every tenth man then separated out and then the remaining 9 of each ten were required to beat the unfortunate ones to death with their fists! Not a 'forgettable lesson.' Now, we pretty much use the term to indicate total destruction, as you have noted.
