Douglas Harper's Etymology Dictionary
1832, from lock (v.) + -able. Related: Lockability.\n
Wiktionary
a. Capable of being locked.
Usage examples of "lockable".
All dress uniforms, garrison uniforms, and personal, non-issue belongings went into lockable chests for storage in a Camp Ellis warehouse.
Unlike most buildings in Erdom, though, this one was not open or covered only with a blanket but had an actual lockable door of wood.
Another wall was given over to a battery of lockable metal cabinets of the rental left-luggage kind commonly found in railway stations.
All four doors are lockable and we will remove the keys after they have been locked.
Though completely walled on three sides by lockable storage compartments for less bulky cargo, the tiny room efficiently contained enough space for a desk and viewer table.
Inside, instead of two benches for the prisoners as I had expected, it had a tiny corridor and six internal cells each with a lockable door.
The building was a converted police command post from the early days of Islendian colonization, and had numerous closets, lockers and offices, most now converted into open space, some left as lockable cubbies for trysts.