-eaux is a common ending for historically Cajun surnames like Babineaux, Boudreaux, Breaux, Marceaux, Robicheaux and Thibodeaux, amongst others. Despite its somewhat confusing appearance, this combination of letters is pronounced with a long "O" sound (IPA(key): /oʊ/).
Although there is debate about the exact emergence of this spelling in the United States, it has been claimed that this spelling originated from English illiterate people having to make an "x" mark at the end of their printed name in order to sign a legal document. Since many Cajun names of French origin already ended in "-eau," the names' endings eventually became standardized as "-eaux." Note however that in French, "-eaux" is the plural form of nouns ending in "-eau".
This claim has been disputed by Carl Brasseaux, who insists that the "-eaux" ending was one of many possible ways to standardize Cajun surnames ending in an "O" sound. Brasseaux claims that Judge Paul Briant is most responsible for the "-eaux" ending during his oversight of the 1820 U.S. Census in Louisiana and that the "x" ending is completely arbitrary.[1]
Several surnames end in -eau (the standard French spelling) especially with names that start with "C" as in Cousineau, a common Cajun surname.
The "eaux" ending is also light-heartedly used among residents of south Louisiana as a marker of their Cajun heritage, particularly at sporting events for Louisiana State University and the University of Louisiana at Lafayette on signs like "Geaux Tigers" or "Geaux Cajuns.", being pronounced as "Go Tigers" or "Go Cajuns" even though such spelling would render it spoken as "Jo"/"Zho" instead.
Steve-O's line of shoes, labeled "Sneaux Shoes", are also (snow shoes).