On Sat, 28 Oct 2017, William Cheswick wrote:

> The third character was “g”, and the ensuing “log" command crashed the 
> server at SRI. AsI recall, the connection was made from UCLA to SRI. 
> Leonard Kleinrocktells this story sometimes.

Thanks; here we are:

https://en.wikipedia.org/wiki/Leonard_Kleinrock#ARPANET

The first message on the ARPANET was sent by UCLA student programmer 
Charley Kline, at 10:30 p.m, on October 29, 1969 from Boelter Hall 3420, 
the school's main engineering building.  Supervised by Kleinrock, Kline 
transmitted from the university's SDS Sigma 7 host computer to the 
Stanford Research Institute's SDS 940 host computer.  The message text was 
the word "login"; the "l" and the "o" letters were transmitted, but the 
system then crashed.  Hence, the literal first message over the ARPANET 
was "lo".  About an hour later, having recovered from the crash, the SDS 
Sigma 7 computer effected a full "login".  The first permanent ARPANET 
link was established on November 21, 1969, between the IMP at UCLA and the 
IMP at the Stanford Research Institute.  By December 5, 1969, the entire 
four-node network was established.

-- 
Dave Horsfall DTM (VK2KFU)  "Those who don't understand security will suffer."