Meaning: A slang commonly used as a theft of food between friends or someone else. Originating from an American Streamer, Fanum, this slang became an internet meme. Soon, Gen Alpha then popularized this slang even further, particularly employing the term.
For example, if someone says "Fanum Tax", that means that they stole your precious food.
Another example: "Officers, those guys FANUM TAXED my french fries. Do me a favor, can you officers FANUM TAX them back?"