Wowser was originally a slang expression, most commonly heard in Australian and New Zealand English. It originated in Australia, at first carrying a similar meaning to ‘lout’, i.e. an annoying or disruptive person, or even a prostitute. In around 1900 it shifted to its present meaning: one whose sense of morality drives them to deprive others of their sinful pleasures, especially liquor. The term was particularly applied to members of temperance groups such as the antipodean branches of the Woman’s Christian Temperance Union.
John Norton, (25 January 1858 – 9 April 1916), editor of the Australian scandal newspaper, Truth, claimed he first used the word in 1899, a claim supported by the OED. However some authors claim that the present meaning originated from an Australian temperance slogan, “We Only Want Social Evils Remedied.” This apparent backronym is considered a “less credible provenance” by the ANU.
"Wowser" was frequently used by artist and author Norman Lindsay, who fought many battles with "Wowsers" over the sexual content in his art and writing.
The Australian writer C.J. Dennis defined it thus: ‘Wowser: an ineffably pious person who mistakes this world for a penitentiary and himself for a warder’. Historian Stuart Macintyre argues, “the achievements of the wowsers were impressive;” they passed laws that restricted obscenity and juvenile smoking, raised the age of consent, limited gambling, closed down many pubs, and in 1915–16 established a 6 pm closing hour for pubs, which lasted for decades.
Americans rarely use the word. However it appears several times in the works of H. L. Mencken:
"In the same way the Archidamian War is more interesting than the fiscal cares of the Four Hundred, and the craft of Pericles takes precedence of his abilities as tax-collector and wowser." American Mercury "The Greeks"