[ih] question re "F" in RFC 819 name/address example

[gfscho at wm.edu]

Dear Internet historians:

Question:

In RFC 819, Jon Postel explains the difference between the 
ARPANET naming convention and the proposed Internet naming 
convention (the DNS) using this address comparison -

ARPANET Convention:   Fred at ISIF
Internet Convention:  Fred at F.ISI.ARPA

What does the "F" stand for in these addresses?

And, less important but also of interest to me, did "Fred" 
refer to anyone in particular or was Postel just using a 
generic name here?

Many thanks if anyone can answer these questions.

Best,
Gretchen Schoel
American Studies Program
College of William and Mary
Virginia