Onomatopoeia is a word that is new to me, but not to my wife. For some reason she learned it in middle school, and it stuck with her many years later. It is just one of those words that once you know it, you know it forever. Onomatopoeia is like a song that gets stuck in your head, and you cannot get it out.
Any word is an onomatopoeia if it refers to a sound or action that the word is describing or referencing. If you say:
“The wolf howled all night.” the onomatopoeia in the sentence is “howled.”
“She was so cold that her teeth chattered.” the onomatopoeia in the sentence is “chattered.”
“That darned duck quacked for hours!” the onomatopoeia in the sentence is “quacked.”
“Susie could not stop hiccupping.” the onomatopoeia in the sentence is “hiccupping.”
The word onomatopoeia is Greek and means “to make names.” It originates with “onoma” which means “name,” and “poiein” which means “to make.”
And the pronunciation is “a-na-ma-te-pe-a”
And if you learn to make poems out of onomatopoeias, then you are writing onomatopoetically.

Inflammable is a debated word perhaps because it seems that flammable and inflammable have the same meaning. Some dictionaries list both words and define them as having the same meaning, which is odd given parallels which the define as antigrams. We would argue that they are used interchangeably, but do not have the same meaning. Examples of opposite meanings would include:
Capable versus Incapable – If a person can do something versus cannot do something.
Solvent versus insolvent – A business is solvent when it can pay its debts, it is insolvent when it cannot pay its debts.
Conspicuous versus inconspicuous – A thing stands out or does not stand when seen.
Destructible versus indestructible – Something is made cheaply or made well.
The Latin language is to blame for the confusion because in Latin it would have been enflame, which led to inflame. Usually a prefix of “in” means “the opposite of something.”
The correct word to use without confusion is nonflammable and not inflammable. Nonflammable items would obviously be glass, steel, concrete, and asbestos. In the past there was a movement by the National Fire Protection Association to only use flammable to avoid confusion, but the public seems to be incapable of making the change.