Why do “flammable” and “inflammable” mean the same thing, or is there a difference?

Question

Edit: SERIOUSLY, THANK YOU—

BTW my confusions stems from them having the same meaning online

Flammable: “easily set on fire”
Inflammable: “easily set on fire”

Definitions from Oxford Languages

In: Other

Answer 1

Holy snap sticks I always thought inflammable means it can not catch fire. Geeeeez 40 years of being an avid reader and I never picked that up