This is the 2144th most frequent Japanese word.
挟ん
The Japanese word "挟ん" is the continuative form of "挟む," meaning "to pinch," "to hold between," or "to insert."
The term "挟んで" here denotes the act of placing something physically between two objects.
本とノートの間にペンを挟んでおいた。
I placed a pen between the book and notebook.
Here, "挟んだ" metaphorically refers to inserting one's idea or comment into an ongoing dialogue.
彼は会話に自分の意見を挟んだ。
He inserted his opinion into the conversation.
In this case, "挟んで" conveys the accidental trapping of an object between two things.