Colloportus

A colloportus is A charm which locks doors magically so that the door cannot be opened manually.

Co·llo·por·tus
/kəˈlō’pôrt’əs/
noun

Colloportus History
The Locking Charm, taught to students at Hogwarts School of Witchcraft and Wizardry during their first-year Charms class from The Standard Book of Spells, Grade 1. The counter-charm for this spell is the Unlocking Charm (Alohomora).

Colloportus Etymology 
From the Latin prefix “collo-” meaning “to bind together” and the Latin “portus” meaning “door.”