The word corpulent comes from the Latin corpulentus, meaning "fleshy" or "fat", which itself derives from corpus ("body") plus the suffix 'ulentus ("full of" or "abundant").  It entered English in the late 14th century via Old French (corpulent), ultimately describing someone or something with a large, bulky body, stemming from the same root as words like corpse, corporation, and corset. 

According to the Oxford English Dictionary (OED) and related sources, the word corpulent first appeared in English in the Middle English period (around 1398) in a translation by John Trevisa.  It came from Old French and Latin, meaning "fleshy, portly, or stout," describing someone with a full body, often linked to wealth in earlier times. 

Examples of "corpulant" used in a sentence: 
"I assumed Troy was referring to the corpulent kid."
"Shannon Oliviera was a rather corpulent woman and she was proud of it." 
"He was not obsessed with corpulent women; he had simply never noticed that she was fat." 
"The audience thought the corpulent soprano they'd cast was hilarious as Violetta." 
"Edward was corpulent, had heavy unshaven jowls and dragged one foot because his shoe had no lace." 
"Throughout history, many political leaders were corpulent, such as the Roman Emperor Vitellius, King Henry VIII, and President William Howard Taft."  

Just the facts:

CORPULENT Definition & Meaning - Merriam-Webster

CORPULENT Synonyms: 85 Similar and Opposite Words | Merriam-Webster Thesaurus