The “correct” usage of “decimation” has been a point of contention in the linguistic community for some time, sparking debate between stiff-necked prescriptivists and carefree descriptivists on what it actually means.
As with all etymology, it’s easiest to begin with, you got it, the beginning. Decimation as far as the English language is concerned, first stems from the Latin “decimus“, meaning a tenth. “Decimāre” stems from this, meaning to take or offer a tenth part – most commonly confused as strictly associated with the Roman military punitive measure of “decimatio“, whereby insubordinate or cowardly cohorts of a legion drew a lottery. One out of every ten straws were shorter than the others, sentencing that legionary to be beaten, stoned or stabbed to death by his comrades. This practice grew rarer after Rome transitioned from republic to empire, and rarer still after its fall: however there are instances as late as WWII, where Soviet commanders utilised the method during the Battle of Stalingrad (1942-3) to tackle desertion rates.
Albeit, with this presumption in mind, it is also important to note that the influences leading to the term in English include “decima“, a tithe or to tithe. A tithe is a levying of money or produce from an area to the state or, most commonly in 16th Century Europe when the term “decimate” was first recorded, to a religious body. The word “tithe”, synonymous with this meaning of decimation, has a similar origin in that it stems from the Old English “teogoþa“, again, translating as a “tenth”. A later example of this is in 1655, whereby Cromwell implemented his “Decimation Tax”, aimed at Royalists post-English Civil War to fund a homeland militia, equating to ten percent of their income.
It is curious to note that the Latinate “decimate” is widely considered archaic and obsolete, whereas the Germannic-origin “tithe” remains rare yet relevant. This is most likely due to certain religious institutions retaining the term and curious preference of the term in historic referencing. At least there will always be decimals.
The first recorded use of decimate’s destructive meaning in English wasn’t until considerably later, in the 1660s and this time, the definition seems to have shifted toward “to destroy a large but indefinite amount of” which coincides with the popular modern perception of the word. Some speculate that this may have stemmed from a misconception that the meaning was “to reduce to one tenth” rather than “to reduce by one tenth”, and this remains cited as an archaic definition of the word in many places.
Another theory is that the word, over time, has become entwined with “devastate” – again, Latinate, stemming from “de-“, “thoroughly” and “-vastare“, “lay waste”. This is first recorded in the English lexicon at a similar time to the comparable meaning of “decimate”, which leads me to believe that this is a viable confusion made at the time which has had permanent effect on the definition.
It is important to note that language inevitably evolves due to a variety of circumstances over time, predominantly due to connotations – these are ideas and feelings exuded from a word, as opposed to their literal meaning (denotation), which warps the manner in which we perceive it.
Reflecting on this, the staunch prescriptivists certainly have a leg to stand on in insisting that decimation relates to destroying or taking one tenth, yet that doesn’t stop their interpretation bordering on archaic anyway. Language is inconsistent and fickle, and is only as correct as how your average person uses it.