Why do the words "inflammable" and "flammable" mean the same thing?

I attended an introductory course on the Laws and Regulations on Scheduled Waste in Malaysia recently and I was particularly annoyed when the trainer highlighted a "mistake" in the English version of the Environmental Quality Scheduled Wastes Regulations. She ridiculed the use of the word "inflammable" to mean "easily burst into flame" in the legal document and wondered why such "obvious" mistake can escape the eyes of so many law practioners. I immediately objected to her interpretation and pointed out that the use of the word "inflammable" is correct in its context, but unfortunately she did not believe in me.

First of all, you need to believe that the lawyers are not idiots and the use of correct terms in a legal document is of paramount importance to them. So, the probability of lawyers making such an "obvious" mistake is practically zero. So, if you can accept that lawyers are not stupid, move on to my next paragraph, else you may stop reading here.

If the use of the word "inflammable" is correct, what is the fallacy in the trainer's interpretation of the word? To answer this question in full, you need to have some understanding on the etymology of the words "inflame", "inflammable", "flame", and "flammable".

Contrary to popular belief, the word "inflammable" is not the negative form of "flammable" as the word "inflame" is not formed by the Latin prefix "in-" and the verb "flame". It is, in fact, a word on its own right. The word "inflame" was first used by John Wycliffe in his English translation of the Bible in 1382.

Loo! forsothe the day shal cumme, brennynge as a chymney; and alle proude men, and alle doynge vnpite shuln be stobil; and the day cummynge shal enflawme hem, saith the Lord of oostis, whiche shal not leue to hem rote and buriownyng. (Malachi 4:1)
in which Wycliffe obviously meant to use the word to convey the meaning of "burst into flames" or "to set ablaze". Therefore, naturally, adding a suffix "-able" to the word "inflame" has the following effect:

"inflame" + "-able" = capable of being inflammed
In the history of the English language, this combination was first used in 1605 in a chemistry book.

1605 Timme Quersit. i. xiii. 54 The sulphurous substance and inflamable matter.
Next, I would like to touch on the word "flammable" which is obviously formed as follows:

"flame" + "-able" = capable of emitting flame = "inflammable"
The word "flammable" was first found in a 19th century translation of Lucretius by Thomas Busby, about 200 years after the word "inflammable" was introduced by Timme.

1813 Busby tr. Lucretius I. 731 That igneous seeds, no longer linked To matter flammable, become extinct.
I hope by now you are convinced that the words "inflammable" and "flammable" carry exactly the same meaning.


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