Claim: The term "hoity-toity" comes from the French words haut toit, meaning "high roof."
The expression "hoity-toity," for "pretentious," comes from the French hauttoit — highroof — from which the pretentious looked down on the literally "lower" classes.
Origins: In common English speech, "hoity-toity" is an adjective used with disdain to refer to the pretentious, those who put on a show of pretending to possess refinement and sophistication (similar to "highfalutin"). So, some people naturally assume that such an unusual expression, referring to the cultured, must itself have a cultured origin — in this case a French-language reference to the (literal) upper class, people who looked down
upon others from atop their high roofs (i.e., haut toit).
"Hoity-toity" has nothing to do with French (or the French), however. The expression comes from our penchant for creating rhyming phrases such as "loosey-goosey" or "helter-skelter," and in this case its base is "hoit," an obsolete 16th century verb whose meaning is "to play the fool" or "to indulge in riotous and noisy mirth." ("Hoity-toity" was more commonly used to describe those who engaged in thoughtlessly silly or frivolous behavior before it became more of a synonym for "pretentious.") Attempts to find the word "haughty" to be an ancestor of "hoity-toity" are equally specious.