The idea of local symbols was introduced by M. E. Conway in 1958, in connection with an assembly program for the UNIVAC 1.
In `UNIX Assembler Reference Manual,' Dennis credits Knuth
for numeric temporary labels, with a reference to volume 1
of The Art of Computer Programming.
I'm several thousand kilometers from my copy of Knuth (though
rather nearer to Knuth himself, albeit not within asking
range), so I'll leave it to others to track down the exact
reference.
Norman Wilson
Toronto ON
(temporarily Sacramento CA)