Codicil
CODICIL (Lat. codicillus, a little book or tablet, diminutive of codex), a supplement to a will (q.v.), containing anything which a testator desires to add, or which he wishes to retract, to explain or to alter. In English law a codicil requires to be executed with the same formalities as a will under the Wills Act 1837.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)