Lee E. McMahon (1931-1989) is the person after whom McMahon tournaments are named.
In 1970, McMahon was a research department head at Bell Labs who realized the benefits of the new Unix operating system for text processing. He convinced the management to buy a new PDP-11 computer which became an important milestone in the Unix development.
McMahon's contributions to Unix include implementations of sed (stream editor), grep (grep regular expressions), qsort (quick sort) and comm (data networking).