The full form of ESX is Elastic Sky  X.

VMware has been a vendor of  servervirualization software for a long time. This story will inform about the history of VMware ESX(i) and uncover the various names used in the history of ESX(i).

VMware was founded in 1998. The first ever product was VMware Workstation released in 1999. Workstation was installed on client hardware.

For server workloads VMware GSX Server was developped. This is an acronym for Ground Storm X. Version 1.0 of GSX Server was available around 2001. It was required to install on top of Windows Server or Linux making GSX a Type 2 hypervisor just like Workstation. The product was targeted at small organizations. Remember we are talking 2001!

GSX 2.0 was released in summer 2002. The last version available of GSX Server was 3.2.1 released in December 2005.Thereafter GSX Server was renamed to ‘VMware Server’ available as freeware. VMware released version 1.0 of VMware Server on July 12, 2006. General support for VMware Server ended in June 2011.

However VMware realized the potential of server virtualization for enterprises and was working on development of a type 1 hypervisor which could be installed on bare metal.

‘VMware Scaleable Server’ was the first name of this product currently known as ESXi.  See this screenshot provided by  Chris Romano ‏@virtualirishman on his Twitter feed. This must be around 1999 or 2000.

After a while the name was changed to  ‘VMware Workgroup Server‘. This was around year 2000. Hardly no reference can be found on internet for these two early names.

In March 2001 ‘VMware ESX 1.0 Server‘ was released. ESX is short for Elastic Sky X. A marketing firm hired by VMware to create the product name believed Elastic Sky would be a good name. VMware engineers did not like that and wanted to add a X to sound it more technical and cool. 

VMware employees later started a band named Elastic Sky with John Arrasjid being the most well known member.

ESX and GSX were both available for a couple of years. ESX was targeted at enterprises. It was not untill around 2005/2006 before ESX got some traction and organizations started to use the product.

ESX had a Service Console. Basically a Linux virtual machine which allows management of the host and virtual machines. Agents could be installed for backup software or other third party tools.