According to David R. Wilton, management
consultant and amateur etymologist, the origin and evolution of the word computer
is rather straightforward. Computer derives directly from the Latin computus
and computare. Both Latin words mean the same as the English verb compute:
to determine by mathematical means. Putare means to reckon, and com is an
intensifying prefix. An intensifying prefix heightens or stresses, but does not change the
meaning of the word it modifies; for example, in the word inflammable, in is
an intensifier, and inflammable means easily inflamed.
The use of computer to refer to a person
who does mathematical calculations dates to at least 1646. The verb form to compute
dates from about the same time, with the first recorded usage in 1631.
The Oxford English Dictionary, Second Edition
(OED2) dates use of the word to refer to a mechanical calculating device as 1897, in the
January 22 issue of the journal Engineering. The earliest reference in the OED2
to electronic computer is in 1946. However, from the context of the citation, it is
obvious that the term was in use prior to 1946.
Citations for the term digital computer
are somewhat older than 1946. The OED2 lists one citation, referring to ENIAC, from
a 1945 Applied Mathematics Panel Report, 171.2R, by J. Eckert, et al. From the
context, it is clear that the term was in general use among engineers already. The
retronym analog computer arose around the same time, with the earliest citation in
the OED2 as 1946. (A retronym is a term that previously did not need to exist, but
is coined because of changes in technology or culture.) Prior to the digital age, no one
referred to analog computers because all computers were analog.
In his 1945 paper on the EDVAC, John von Neumann
used the term automatic computing system, which he italicized as a definition.
Eventually, the descriptive adjective in front of
computer was dropped as digital computers became more and more common, driving out the
other usages of the language.
You can find other discussions of the etymology
of words at David Wilton's Etymology