Why is an application called an application?

Solution 1:

According to OED, in computing, application was first applied to functions:

A function performed by a computer to meet a specific user requirement

It is similar to the earlier sense of application: an act of putting to use, specific use.

Then, the meaning of application has extended:

(now usually) a program or piece of software designed to perform such a function (as distinct from software which supports the operating system itself).

In computing, it is first recorded in 1959 [OED]:

This approach to a file maintenance application implies that a number, or ‘batch’ of transactions is collected and sorted into the order of the master file.

_{J. Jeenel, Programming for Digital Computers}

Application program is from 1964. [OED]

Application software is from 1966. [OED]

Solution 2:

The first time I met the term application as a name for a computer program, it was not a term in its own right yet, but it was almost always used in combination with the name of a software development tool, such as code generator or compiler. For example, there were Oracle Forms applications, or C applications, or COBOL applications. In my memory, the term was most effectively made popular by the salesmen who marketed software development tools for developers. It then caught on, and developers began talking about applications instead of programs, because when they presented their code to users, they soon realized that the users are not impressed by the technology that was applied. Over a rather short period of time, the tool names wore off of the expression, an the word application remained alone. The first times when I noticed that the word was used on its own, it disturbed me. I strongly believed that this was not the right way to use the term. Then I too had to give in to the strange logic of human language.

So once again, the difficulty of understanding an IT term is based on 1) the original use being based on programmer's viewpoint entirely and 2) the transition from a programming term to a general term happened so quickly that neither party realized what just happened.

Solution 3:

This is too long for a comment, from Dictionary.com:

1. The act of putting to a special use or purpose: the application of common sense to a problem.

2. The special use or purpose to which something is put: a technology having numerous applications never thought of by its inventors.

Source code is put into a special use/purpose (the compiled, executable product).

An application of source code is the executable product.