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once; some time ago
「一ころ」 has another reading with different meanings.
一ころは毎日ジョギングをしていたが最近は怠けている。
I used to jog every day at one point, but lately I've been slacking off.
一ころ流行したゲームが再び注目を集めている。
A game that was popular some time ago is attracting attention again.
一ころに比べて物価がかなり上昇している。
Prices have risen considerably compared to some time ago.