Old English forbeodan "forbid, prohibit" (past tense forbead, plural forbudon, past participle forboden), from for- "against" + beodan "to command" (from PIE root *bheudh- "be aware, make aware"). Common Germanic compound (compare Old Frisian forbiada, Dutch verbieden, Old High German farbiotan, German verbieten, Old Norse fyrirbjoða, Swedish förbjuda, Gothic faurbiudan "to forbid").
In Middle English the past tense was forbad, the plural forbade, the past participle forbode. Related: Forbade; forbidden. Expression God forbid is recorded by early 13c. Forbidden fruit is from Genesis ii.17.