Sir, Ser, Senior, Señor

Are they really connected, or is the similarity just a coincidence?

It’s possible that, once you combine all these words, it gets easier to see a connection, but… are they really connected, or is the similarity just a coincidence?

You very well know the meaning of the word sir, and probably know that ser is an alternative spelling used quite often in fiction, fantasy, etc. (of course, Game of Thrones and all that kind of stuff come to mind).

Now, the word senior is also used in English to refer to elders in a respectful way. This word undoubtedly comes from the Latin senior, which is the comparative form of senex ‘old’. This is why it is also used to oppose Junior and Senior when talking of a son and a father with the same name: it literally means John ‘the Younger’ and John ‘the Older’.

(By the way, from senex we have senate, because the Roman senatus was at first a literal chamber of elders).

The Spanish word señor ‘mister, master’ also comes from senior, although it is not connected with age, but with respect (after all, that semantic transition makes a lot of sense).

So going back to sir and ser, do they have their origin in the Latin senior? Well, yes, they do, specifically through the fuller word sire, through Old French sire, another form of sieur, which you can connect to monsieur (literally my sieur). This sieur is the French evolution from Latin senior.