「アイ・ディー＝ID」が身分証明書だとすると元はidentification card 「アイデンティフィケーション　カード」Identificationは名詞で、動詞はIdenti-fy「あるモノ・人が何か、誰かを確かめる」という意味。

I want to tell you about my recent experience voting for our new governor. When I arrived at the voting place, I realized I forgot an important document. I thought I couldn't vote because it was almost closing time. I was worried because I thought proving who I am would be very difficult.