To intervene in a dispute, or in a conversation.
To interrupt a conversation by introducing a different subject or making a comment.
To insert something (or oneself) between other things.
To be inserted between parts or things; to come between.
To offer (one's help or services).
To take a customary action to ward off some misfortune that is believed to be attracted by a presumptuous statement.
Hopefully; a self-directive to undertake the customary action to ward off bad luck.