This question could be split into two types of terms: new expressions & old expressions.
For new expressions one could open Google &/or Baidu go to "News" (资讯) and then "Order By Date" (按时间排序).
Other than this I'm not sure if there are any better options.
As for old expressions: there was an answer on here before that mentioned using 漢籍全文資料庫 to find the earliest usage in historical documents.
Again, I don't know if this is the optimal way of doing this.