Or pg if the context is clear enough.

That might be more than slightly confusing here on Hacker News.

psql? pgsql?

Now we wait for pg to release his Arc lisp based database system called pgsql

Neither works: psql is the bundled postgres shell and (pl/)pgsql is posgres's procedural SQL extension (inspired by Oracle/s pl/sql) so both are pretty ambiguous.

pgsql is exclusive to postgresql, and from the context, it should very easy to know if you talking about the programming language or postgresql

pg sequel or pg ess-queue-el

are both very good, short, and difficult to confuse with another project or product

i think psql refer specifically to the command line tool of pgsql