Maybe this will explain :
https://en.wikipedia.org/wiki/Httpd
CERN httpd is discontinued, but yes they do have something in common as well,
As far as the difference between security with httpd, and nginx:
I agreed with Carpetsmoker, they both seem to be secure, or have the
same security potential, this mostly depends on how one configures
the system, IE: A poorly configured system, and firewall, using Nginx,
could be very insecure, but the same, using httpd, if the firewall, etc is
not configured correctly it could be very insecure.
Both, in a properly configured system are very secure.