IPA: /ˈwɔːrəntər/
KK: /ˈwɔːrəntər/
A person who guarantees or promises to ensure that something is true or valid, often related to a contract or agreement.
The warranter assured the buyer that the product was free from defects.
Warranter → It is formed from "warrant" (from Old French *garant*, meaning to guarantee or protect) and "-er" (meaning a person who). A warranter is a person who guarantees or provides assurance.
Think of someone who 'guarantees' something — that's what a warranter does, as they are the person providing assurance.