Issues of elastic scalable and secure applications running on a shared computer system existed long before cloud computing. The Wikipedia's definition is:
Cloud computing is the use of computing resources (hardware and software) that are delivered as a service over a network (typically the Internet).About all that seems to be new is the use of the Internet as the network, the large scale of the servers used and the number of different servers involved.
The Wikipedia points out that:
The underlying concept of cloud computing dates back to the 1950s; when large-scale mainframe became available in academia and corporations, accessible via thin clients / terminal computers. ...