Origins
A prince was never meant to be a king's son.βββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ The word comes from Latin princeps β prΔ«mus ('first') plus capere ('to take') β meaning 'first person' or 'chief'. It was a title of rank, not of blood.
In the Roman Republic, the princeps senΔtΕ«s was the most senior senator β the first to speak in debate. When Augustus seized power in 27 BCE, he rejected rex ('king') as too provocative and styled himself princeps instead. First citizen, not monarch. The fiction held for centuries; the early Roman Empire is called the Principate.
Old French inherited prince from Latin and began shifting its meaning. Feudal Europe needed a word for rulers below the king, and prince filled that role. By the 13th century, when the word entered English, it could mean a sovereign, a feudal lord, or the son of a king.
Scientific Usage
The word family radiates outward. Principal means 'first in importance' (a school principal is the 'first teacher'). Principle means 'first rule' or 'foundation'. Principality means a territory ruled by a prince β Wales is technically a principality.
Machiavelli's Il Principe (1532) returned the word to its Roman roots. His prince was not a king's child but a ruler who seizes and holds power β closer to the original princeps: the one who takes first.