Every Man His Own Broker book, published 1775, contains the first usage of the words: Bull and Bear as types of investors. Written by Thomas Mortimer, published by S. Hooper in London.
The words Bulls and Bears are mentioned several times throughout the book, including the Preface. This book has some great quotes. In the Preface he talks about the "Act for the better preventing the infamous practice of Stock-jobbing; by which the most palpable and glaring frauds then in vogue, were indeed suppressed: the Bubles burse, and the Racehorses of Exchange Alley, expired with the date of that act; but BULLS and BEARS still exist in full vigour."