a person who tends to worry habitually and often needlessly; pessimist; fussbudget.
Origin of worrywart
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
1956, from comic strip "Out Our Way" by U.S. cartoonist J.R. Williams (1888-1957). According to those familiar with the strip, Worry Wart was the name of a character who caused others to worry, which is the inverse of the current colloquial meaning.
Online Etymology Dictionary, © 2010 Douglas Harper