Elastic multitenancy refers to the idea that a system can accommodate multiple client storage resources together ("multitenant") and offer on-demand changes within the system ("elastic").
The term is commonly used in modern cloud computing and network virtualization.
Techopedia explains Elastic Multitenancy
A system that supports elastic multitenancy allows a client’s separate storage resources to be treated completely independently and securitized from one another, even though they may be held in the same servers and hardware pieces, in the same IT room and even on the same sets of drives. This setting has its own benefits and disadvantages, such as competitive costs, along with some security issues that customers may have. Moreover, the elasticity of a multitenant system is the extent to which resources can be redistributed among the tenants quickly and efficiently.
Cloud experts talk about "on-demand systems" that allow clients to add or remove services just by calling or choosing an online option. Multitenant systems often enable this elasticity because, with shared resources, it is possible for the cloud provider to accommodate such on-demand changes. Experts use terms like "rapid elasticity" and "resource pooling" to describe these kinds of scalable and versatile arrangements. Many of these are governed by specific service-level agreements that show customers what they can get from a cloud provider.