1. 對drain的理解：是指浪費或者使。。。流失
根據google字典，drain作為名詞，指a thing that uses a lot of the time, money, etc. that could be used for something else 消耗；耗竭；耗費 singular ~ on sb/sth
Military spending is a huge drain on the country's resources. 軍費開支是對國家資源的巨大耗費。
Idiom: (go) down the drain informal
(to be) wasted; (to get) very much worse 被浪費掉；變得非常糟糕
2. a relic of the past, 這個比較好理解，就是已經成為過去的事物，失去時效性，不再符合目前狀況的事物。