案 originally refers to a long wooden table (like a writing desk), and by extension it came to mean the documents or records kept on that desk, then the legal case or incident recorded. In modern Chinese it is most commonly used in legal and administrative contexts: 案件 (legal case), 档案 (file/archive), 方案 (plan/scheme). It can still mean 'table' in literary or antique terms (e.g. 伏案 'bend over one's desk'). This multiple-meaning network is not captured by a single English word.