Belfry

The openings may be left uncovered but are commonly filled with louvers to prevent rain and snow from entering and damaging the bells.

The word belfry comes from the Old North French berfroi or berfrei, meaning 'movable wooden siege tower'.

the cognate bergfried), combining the Proto-Germanic bergen, 'to protect', or bergaz, 'mountain, high place', with frithu-, 'peace; personal security', to create berg-frithu, lit.

[2] Merriam-Webster explains the transformation by the fact that the initial word was later used for different types of towers and protective buildings, many containing bells.

[3] [1] In larger towns, explains Kingsley Amis, watchmen placed in towers were also on the lookout for fires.