expression
Emphasizes that something happens or is done a single time, and no more.
その映画は一度だけ見た。
I saw that movie only once.
一度だけでもいいから、富士山に登ってみたい。
I'd like to climb Mt. Fuji, even if it's just once.
Combination of 一度 (いちど, 'once') and the particle だけ ('only').