IPA: /ˈkæt.əl.ɒ.ɡər/
KK: /ˈkætəlɒɡər/
A person who organizes and maintains a list of items, often in a systematic way, such as in a library or store.
The cataloguer carefully arranged the new books on the shelves according to the library's system.
Cataloguer → It is formed from "catalogue" (from Latin *catalogus*, meaning a list or register) and "-er" (meaning a person who). A cataloguer is a person who creates or maintains a list or register of items.
Think of a person who makes a 'list' ('catalogue') of items — that's what a cataloguer does.