ETYM French.
1. A cylindrical tower used for storing silage.
2. An underground structure where ballistic missiles can be stored and fired.
Storage pit or building for silage.
In farming, an airtight tower in which silage is made by the fermentation of freshly cut grass and other forage crops. In military technology, a silo is an underground chamber for housing and launching a ballistic missile.

Town in Oklahoma (USA).