wowser · noun1
From UK dialect. Australian from late 1890s. John Norton, an early enemy of wowsers, claimed it to be an acronym for "We Only Want Social Evils Remedied", but that is likely a folk etymology. A story has it that gospellers in the streets of Clunes, Victoria in the 1870s were called rousers but one of the town councillors had a speech impediment and couldn't pronounce his "R"s, thus giving wowser. (Reference: Bill Wannan, Australian Folklore, Lansdowne Press, 1970, reprint 1979 →ISBN, under "Wowser", page 568.)
wowser · noun, interjection2
Origin unknown. # (US) A fierce imaginary animal. #* 1968, Squire Omar Barker, Rawhide Rhymes: Singing Poems of the Old West, page 10: Well, a wowser is the critter That the nester's little daughter is afraid will come and git her In case she fails to wash her neck and mind her pa and ma, For what the ring-tailed wowser likes is little gals to chaw. At least she's heard the cowboys thus describe this wondrous beast With one green eye a-lookin' west, a red one lookin' east. But speaking scientifickly, the wowser is a cross Between the cattywampus and and the dry-land albatross With parts of grizzly bear throwed in, and just enough of 'coon To give him rings around his tail, like rings around the moon. From wow, with the "-ser" added to provide emphasis.
Etymology from Wiktionary, CC BY-SA 4.0.