In what year did ARPANET carry its first message and Unix development begin?

1969 → tub · ship.

On 29 October 1969, ARPANET — funded by the U.S. Defense Department's Advanced Research Projects Agency — sent the first host-to-host message between Leonard Kleinrock's lab at UCLA and Stanford Research Institute. The operator typed "LOGIN"; the link crashed after the first two letters, so the Internet's first word was an accidental "LO". ARPANET pioneered packet switching — chopping messages into addressed packets routed independently — the idea that underpins all networking today. The same year, after the failed Multics project, Ken Thompson and Dennis Ritchie began building Unix at Bell Labs on a spare PDP-7. Peg 19 · 69 → tub · ship: a toy ship in a bath tub.