Sonar as an acronym preceded radar.  It was "originally an acronym for SOund
Navigation And Ranging."
According to Wikipedia, however,:

During the 1930s American engineers developed their own underwater sound
detection technology and important discoveries were made, such as
thermoclines <http://en.wikipedia.org/wiki/Thermocline>, that would help
future development. [8]
<http://en.wikipedia.org/wiki/Sonar#cite_note-7>After technical
information was exchanged between the two countries during
the Second World War, Americans began to use the term *SONAR* for their
systems, coined as the equivalent of RADAR<http://en.wikipedia.org/wiki/Radar>
.

stevo

On Wed, Feb 2, 2011 at 10:25 AM, Logan Kearsley <[log in to unmask]>wrote:

> > At least in the case of "-coholic", I'm pretty sure that's due to the
> > portmanteau "chocoholic" causing it to be re-analysed. "-dar" I'm not
> > so sure has an independent existence: there's the portmanteau
> > "gaydar", of course, but aside from nonce terms that still act as
> > portmanteaus (first unit shares the /Ei/), I can't really think of
> > anything else following the pattern.
>
> There's "lidar", so at least 1. But that's more of an acronym that
> happens to share the same last three words than it is a re-analysis of
> "-dar". Sonar might be a good example, dropping the 'd'.
>
> -l.
>