button%20up

To remain silent, especially in order to keep a secret or to avoid saying something inappropriate.

To fasten with a button or buttons.

“Button up your shirt cuff. It has come undone”

To fasten all the buttons on a coat, or similar item of clothing, to keep warm.

“Button up well. It's freezing outside today.”

To conclude; to finalize; to put the finishing touches (on)

“It's time to button up the meeting.”

To seal off (a military vehicle or facility).