For Catholics, the tabernacle is the receptacle in which the Eucharistic bread is kept, outside of Mass.
The practice began so that Communion could be taken to the sick and the dying who couldn't come to Mass.
"Tabernacle" comes from a Latin word that means a small tent, hut, or similar structure. Thus, it is the place where Christ is present in the Blessed Sacrament.
The early Christians didn't use a tabernacle. Theologian Fr. Karl Rahner suggested that it was because they believed Jesus was in the consecrated bread and wine only when the community was gathered together.
During the Middle Ages, there was no designated container in which the Blessed Sacrament was kept. But the Fourth Lateran Council (1215) determined that the consecrated hosts should be kept in a secure receptacle. The result was the tabernacle.
- Little White Book, Diocese of Saginaw