The earliest known use of the verb whew is in the late 1600s. OED's earliest evidence for whew is from 1684, in the writing of Thomas Otway, playwright and poet. whew is perhaps an imitative or expressive formation. See etymology. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.