This is the 18696th most frequent Korean word.
신었다가
"신었다가" means "wore (shoes) and then" or "put on (shoes) and then."
The word '신었다가' indicates an action of putting on shoes (sneakers, in this case) followed by a change or reverse action of taking them off.
나는 운동화를 신었다가 벗었어요.
I put on sneakers and then took them off.
The word '신었다가' is used to show the sequence in which boots were first worn and then replaced with slippers.
그는 부츠를 신었다가 슬리퍼를 신었어요.
He put on boots and then changed to slippers.
Here '신었다가' signifies an intermediate action where socks were put on as a precursor to wearing shoes.