How is “go steady” used?

In Lolita (1962), one line is: “...Kenny's gonna ask her to go steady tonight.”

Which movie is “go steady” from?

The clip at the top of this page is from Lolita (1962).

...Kenny's gonna ask her to go steady tonight.

5 作品で登場 · 1 本目

to have a romantic or sexual relationship with sb, in which you see the other person regularly

くだけた · 古風 · 5 本の映画に登場

オックスフォード映画の 100%
to have a romantic or sexual relationship with sb, in which you see the other person regularly
...Kenny's gonna ask her to go steady tonight.

定義：Oxford Advanced Learner's Dictionary 第 9 版