Merriam-Webster's Collegiate® Dictionary, 11th Edition
PRIMER
I. noun
Etymology: Middle English, layperson's prayer book, from Anglo-French, from Medieval Latin primarium, from Late Latin, neuter of primarius primary
Date: 14th century
a small book for teaching children to read, a small introductory book on a subject, a short informative piece of writing,
II. noun
Date: 1819
a device for priming, material used in priming a surface, a molecule (as a short strand of RNA or DNA) whose presence is required for formation of another molecule (as a longer chain of DNA)