What does appendix mean?
The definition of appendix
Ap*pen”dix, n.; pl. E. Appendixes, L. Appendices(#).
Etym: [L. appendix, -dicis, fr. appendere. See Append.]

1 Something appended or added; an appendage, adjunct, or concomitant. Normandy became an appendix to England. Sir M. Hale.
2 Any literary matter added to a book, but not necessarily essential to its completeness, and thus distinguished from supplement, which is intended to supply deficiencies and correct inaccuracies.

Synonyms
— See Supplement.