IPA: /ˈwɜːriər/
KK: /ˈwɒr.i.ər/
A person who feels anxious or concerned about things, often without a good reason.
She is such a worrier that she often loses sleep over small problems.
Worrier → It is formed from "worry" (from Old English *wyrgan*, meaning to strangle or choke) and "-er" (meaning a person who). A worrier is a person who is choked or strangles themselves with anxiety or concern.
Think of someone who is 'strangled' by their own thoughts and worries — that's why a worrier is a person who is anxious.