IPA: /ˈleɪbələr/
KK: /ˈlæbələr/
A person or device that attaches labels to items or products, often used in packaging or organization.
The labeller quickly organized the boxes by adding labels to each one.
Labeller → It is formed from "label" (from Old French *label*, meaning a small note or tag) and "-er" (meaning a person who). A labeller is a person who applies or creates labels.
Think of a person who creates or applies a 'small note' ('label') to something, which is what a labeller does.