As far as American English is concerned, "flammable" has legal consequences: The word "inflammable" is still used when speaking of emotions, "flammable" when speaking of things "capable of being easily ignited and of burning quickly." US Federal law requires the spelling "flammable" to be used on warning labels for such objects. The change from "inflammable" to "flammable" in this meaning was a deliberate reform instituted by the American scientific community and insurance industry.
If you look up the etymology of the terms, you will see that "flammable" is not given simply as "inflammable" with the "in-" dropped. The following are typical of the etymologies given for the two words. From *Merriam-Webster's Collegiate Dictionary,* 11th ed.:
"flammable Etymology: Latin flammare to flame, set on fire, from flamma
"Date: 1813"
"inflammable Etymology: French, from Medieval Latin inflammabilis, from Latin inflammare
"Date: 1605"
There was a discussion about this in the newsgroup alt.usage.english , in which the possibility was raised that those wishing to get rid of the "in-," out of fear that "inflammable" may be mistaken to mean "not easily ignited," may have dropped the "in-" off of "flammable" then looked around for previous uses of the word "flammable" in order to legitimize it. There were indeed very limited uses of "flammable" and "flammability" prior to the 20th century. See the post at
alt.usage.english | Google Groups plsray%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26selm%3Dv8mcvbmni3hfe4%2 540corp.supernews.com%26rnum%3D1
or
alt.usage.english | Google Groups
and the posts before and after it in that thread.
See also
'inflammable' confused with 'not flammable' - an actual example found in print - alt.english.usage | Google Groups
or
'inflammable' confused with 'not flammable' - an actual example found in print - alt.english.usage | Google Groups
for a verified, but *extremely* odd, instance of confusion concerning the two terms.
Raymond S. Wise
Minneapolis, Minnesota USA
E-mail: mplsray @ yahoo . com