What is Blotter?

Legal Definition
A transaction record that covers a specific time period in an organization. Or a paper that prevents ink from bleeding between copies.
Legal Definition
Mer. law. A book among merchants, in which entries of sales, &c.;are first made.

2. This book, containing the original entries, is received in evidence, when supported by the oaths or affirmations of those who keep it. See Original entry.
-- Bouviers Law Dictionary