The Spanish word 'septentrional' meaning 'northern' has a fascinating connection to astronomy through Latin. It comes from the Latin word 'septentrionalis' meaning 'northern', which itself derives from 'septentrio' referring to the 'seven stars' of either the Great Bear (Ursa Major) or Little Bear (Ursa Minor) constellations. The root of this word goes back to Latin 'septem' meaning 'seven', referring to the seven bright stars that make up the Big Dipper asterism within Ursa Major. Since these constellations were used for navigation and were visible in the northern sky, the word evolved to mean 'northern' in general.

Some related Spanish words that share the 'sept-' root meaning 'seven' include 'septiembre' (September, originally the seventh month in the Roman calendar), 'séptimo' (seventh), and 'septenio' (a period of seven years).

English speakers can recognize this etymology through words like 'septenary' (consisting of seven), 'septennial' (occurring every seven years), and 'September'. The astronomical connection is preserved in the term 'septentrion', an archaic word for the northern regions or the north star, though this word is rarely used in modern English.