Berkeley Yacc was originated in 1985 by Robert Corbett (see Corbett 1984). It was originally named “zoo”, but by October 1989 it became known as Berkeley Yacc or byacc.
Berkeley Yacc had three advantages over the ancestral Yacc: it generated faster parsers, it could generate reentrant parsers, and the source code was released to the public domain rather than being under an AT&T proprietary license. The better performance came from implementing techniques from DeRemer and Penello’s seminal paper on LALR parsing (see DeRemer 1982).
Use of byacc spread rapidly due to its public domain license. However, once Bison became available, byacc itself passed out of general use.