IPA: /ˈblɒtə/
KK: /ˈblɒtər/
A book or pad used to absorb ink or record daily events and transactions.
The officer checked the blotter for any recent incidents reported in the area.
Blotter originates from the Middle English word 'blotter', which is derived from 'blot' (meaning to stain or spot) and the suffix '-er' (meaning a person or thing that performs an action). A blotter is thus a thing that stains or absorbs ink.
Think of something that 'stains' ('blot') and 'absorbs' ('-er') — that's why a blotter is used to soak up ink.