The name "flex" itself was based on the name of the original Unix lexer-generator "lex", just like its sibling parser generator "bison" was a play on words of l

The name "flex" itself was based on the name of the original Unix lexer-generator "lex", just like its sibling parser generator "bison" was a play on words of lex's parser generator sibling "yacc" (which stands for "yet another compiler compiler"). Fun fact: one of the original authors of lex was Eric Schmidt, now executive chairman of Alphabet.