“当初”这个词用什么英语单词好？

Initially

当初:
1. originally
2. at that time

Examples:
1. 他当初的积极性已淡下去了.
His original enthusiasm has turned sour.
2. 他当初刚到伦敦时很孤单.
He was very lonely at first when he moved to London.
3. 损害程度比当初预想的要严重得多。
Damage is much greater than was at first anticipated.

当初 [简明汉英词典]
in the first place
originally

at first
originally
at that time
then

originally; at first

at that time