When you say what happened or was the case originally, you are saying what happened or was the case when something began or came into existence, often to contrast it with what happened later.
The plane has been kept in service far longer than originally intended.
这架飞机已超期服役很长时间了。
The castle was originally surrounded by a triple wall, only one of which remains.
这座城堡最初有三面墙环绕,现在只剩下一面了。