OurBigBook
This option is similar to \H title2 argument but it additionally:
  • creates a new ID that you can refer to, and renders it with the alternate chosen title
  • the rendered ID on cross references is the same as what it is a synonym for
  • the synonym header is not rendered at all, including in the table of contents
  • when using -S, --split-headers, a redirect output file is generated from the synonym to the main ID
Example:
= Parent

== GNU Debugger
{c}

= GDB
{c}
{synonym}

I like to say \x[gdb] because it is shorter than \x[gnu-debugger].
renders something like:
= GNU Debugger

I like to say \a[#gnu-debugger][GDB] because it is shorter than \x[#gnu-debugger][GNU Debugger].
Furthermore, if -S, --split-headers is used, another file is generated:
gdb.html
which contains a redirection from gdb.html to gnu-debugger.html.

Ancestors