Flammable and Inflammable

Look at these pairs of words. Accurate and inaccurate. Appropriate and inappropriate. Decent and indecent. You can name many pairs like those I have pointed out. The second word is the opposite of the first, simply by adding the prefix "in".  There is, however, a strange case, in the words flammable and inflammable.

There is no difference in meaning between flammable and inflammable. Both mean burn easily. There is a preference, however,  for flammable in both British and American English. 
   
Actually, inflammable is the original form, derived from the verb inflame. "In" is derived from the Latin preposition meaning en (engulf, endanger, enslave) not the prefix meaning un. But because it’s easy to interpret the in as the common negative prefix in (as in inaccurate, inappropriate), the word has always caused confusion. Therefore it was only a matter of time, that Safety and Fire Protection Agencies and Associations would urged the use of the word "flammable" rather than "inflammable".

Bill Bryson (Dictionary of Troublesome Words, Penguin Reference, 1984) has this to say, "Because the meaning of inflammable is so often misapprehended, there is an increasing tendency to use the less ambiguous flammable. In other cases this might be considered a regrettable concession to ignorance. But it would be even more regrettable to insist on linguistic purity at the expense of safety."