How did horses influence the English words chivalry and cavalier?

Both chivalry and cavalier share a common linguistic origin rooted in the Latin word caballus, meaning "work horse" or "gelding".123

• Chivalry: Derived from the Late Latin caballārius ("horseback rider"), the term entered English via Anglo-French as chevalerie. It originally referred to a body of mounted soldiers or knights. Over time, the meaning evolved from describing a class of horse-mounted warriors to representing the code of conduct, values, and honorable behavior associated with medieval knighthood.2
• Cavalier: This term also traces back to caballārius. It initially described a gentleman trained in arms and horsemanship or a mounted soldier. While it once denoted gallantry, the term was later used by Puritans to disparage the royalist followers of Charles I. This historical context shifted the adjective’s meaning, leading to its modern usage to describe someone who is flippant or dismissive of serious matters.134

Ultimately, both words reflect how the historical necessity of the horse in warfare and social status shaped the language used to describe soldiers, gentlemen, and their respective codes of behavior.123