Origin: Germanic Old English prefix
Forbidden has 3 different meanings across 1 category:
past participle of forbid
"The king declared that anyone entering the palace without an invitation would be punished, so the gates remained forbidden to all strangers."
excluded from use or mention
"forbidden fruit"
"in our house dancing and playing cards were out"
"a taboo subject"
Not allowed; specifically disallowed.
"The teacher marked my essay forbidden because I copied too much from another student's work."
In plain English: Forbidden means something that is not allowed to be done because it breaks a rule.
"The school rules state that bringing phones to class is strictly forbidden."
Forbidden is the past participle of the verb forbid and a doublet of the word verboten. The term shares roots with similar words in German, Dutch, Swedish, and West Frisian.