The core of "rarefied" lies in the Latin words "rarus" and "facere," which together formed "rarificare," meaning "to make thin or rare,"  The word then passed through Old French, where it became "raréfier," further evolving into Middle English "rariefien". Initially, "rarefied" meant "made less dense," like air at high altitudes. Over time, it gained other meanings, including "exalted" or "of high intellectual or moral value".  Today, "rarefied" is used to describe things that are thin, less dense, or of a high quality, often in a context of exclusivity or elevation. 

The adjective "rarefied" was first used in English in the early 1500s.  It's a past participle of the verb "rarefy", which itself appeared in Middle English in the 14th century,  The Oxford English Dictionary records the earliest use of the adjective "rarefied" in English from 1523, in the writing of John Skelton. 

Examples of rarefied used in a sentence: 
"How does it feel to be breathing such rarefied air?" 
"The debates about the nature of knowledge can seem very rarefied" 
"The Moon has no atmosphere; the Martian atmosphere is highly rarefied." 
"She portrays him as an outsider in the rarefied academic atmosphere of Oxford university."  
"The rarefied book was written in an ancient language that could only be read by a few linguists and historians."  
"When the Olympian won his tenth gold medal, he joined a rarefied body composed of only a small number of athletes." 
"Only a couple of audience members were not confused by the scientist’s rarefied concept."  
"Because Ann and Ted were not used to staying in luxury resorts, they were baffled by some of the rarefied amenities offered to them."
"The singer is one of the few artists to reach the rarefied distinction of having fifteen number one hits."