The word "inhalation" comes from the Latin inhalare, meaning "to breathe in". It is formed from the prefix in- ("in, into") and the verb halare ("to breathe"). The suffix -ation denotes an action or process, making the noun mean "the act of breathing in". 

According to the Oxford English Dictionary (OED), the first use of the noun "inhalation" in English was in the early 1600s, with the earliest specific evidence from 1623 in the writings of lexicographer Henry Cockeram. It was derived from the Latin word inhālātiō.  The verb "inhale" first appeared in English between 1715-1725.  The first recorded use of the verb in the dictionary was in the OED's 1900 First Edition. 

Examples of "inhalation" used in a sentence:  
"The fire killed 36 people, all of whom died from smoke inhalation." 
"The dogs suffered smoke inhalation but were revived at the scene, the spokesperson said." 
"The fire started in the garage and sent one person to the hospital for smoke inhalation." 
"She made no noise except the occasional inhalation and exhalation of air." 
"Treatment includes resting the voice and inhalation of humidified air." 
"Hyperventilation is the repeated inhalation of fast, full breaths of air and rapid exhalation."