The word "ostentatious" traces its roots back to Latin, ultimately steming from the verb "ostendere," meaning "to show" or "to display."  This verb is a frequentative form of "tendere," meaning "to stretch," suggesting an outward and often exaggerated display, or from the Latin word "ostentātus" (meaning "displayed" or "shown"), along with the English suffix "-ious."  The word evolved through Middle French "ostentacion," and into Middle English as "ostentacioun," thus acquiring the sense of pretentious or vulgar display intended to impress others. 

The adjective "ostentatious" was first used in the English language in the late 1500s, specifically in 1590, in the writings of William Segar, according to the Oxford English Dictionary.  

Examples of ostentatious in a sentence:  
"London at the time was a curious mixture of ostentatious wealth hiding harrowing poverty." 
"There is status in ostentatious display."
"That first house was horribly ostentatious." 
"The pulpit is not the place for ostentatious display of one's skill." 
"They do not consider their own large, ostentatious houses common." 
"The ostentatious wealth of the new rich only served to highlight the destitution of the rest of society."