How is “be sweet on” used?

In Downton Abbey: A New Era (2022), one line is: “Weren't you sweet on him once?”

Which movie is “be sweet on” from?

The clip at the top of this page is from Downton Abbey: A New Era (2022).

Weren't you sweet on him once?

3 作品で登場 · 1 本目

to like sb very much in a romantic way

くだけた · 古風 · 3 本の映画に登場

オックスフォード映画の 100%
to like sb very much in a romantic way
Nobody else seems to guess you're sweet on her.
Weren't you sweet on him once?

定義：Oxford Advanced Learner's Dictionary 第 9 版