"Flammable" is, indeed, not a new construction.
Agreed. According to Fowler’s Modern English Usage:
inflame etc.
Inflam(e)able, formed from the English verb, and used in 16th-17th cc., has been displaced by
inflammable adapted from French or Latin.
Inflammable and
inflammatory must not be confused as in
Sir Edmund Carlson declared before an inflammatory audience that in the event of the Parliament of these realms doing certain things that were distasteful to him he would call out his Volunteers. It must have been a supposed ambiguity in
inflammable that led to the coining of the word
flammable. But that could only make things worse, and
flammable is now rare, usually in the compound
non-flammable, a more compact version of
non-inflammable.