Define Inflammable Meaning

I dont understand why flammable and inflammable mean the same when sane and insane mean exactly the opposite things.

That puddle of alcohol is inflammable.

Simon: "Hey philip do you think my ass is inflammable?"

Philip: "Lets find out......."

Simon: "Oh you sh*t head, you just set my anus on fire!"

Simon & Philip: (laughter)

Tom: "Gas is inflammable Bob."
Bob: "Oh yea, that means I can out this fire with it right?"
Bob: "Ut-oh"

Warning, chemical inflammable!

"This is an inflammable computer" said the sales clerk. a week later it overheated and burned the house down.

the cats tail is very inflammable

The gasoline vapors from the ruptured tank were inflammable.

Warning, Chemical is inflammable!