Server applications usually have the 'd' letter appended to signal that it's a daemon tool (doing it's thing in the background). 'http' obviously stands for Hyper Text Transfer Protocol.
To reason to use the name from httpd instead of apache was both a practical and historical choice. In February of 1995, the most popular server software on the Web was the public domain HTTP daemon developed at the National Center for Supercomputing Applications, University of Illinois. Development of that httpd had stalled after 1994. The term "httpd" was already quite commonly accepted among web masters.
The official name of the Apache project is "The Apache httpd server" anyway, so it already gives a hint. It grew out of the NCSA httpd project (there's the hint again). Even more, it explains what the deamon does (in a certain way), it can be the same for different version of a web browser application or even a different web server. Apache itself comes from "A PAtCHy server", so it was always meant a httpd server, though a patchy one.