Common case: I came to live in Southern Spain some time ago and I'm learning Spanish here. I keep hearing every once and again the word 'illo'. It seems to be used as a vocative to call people or just give emphasis to a sentence. But what does that word mean? Where does it come from?
Indeed, if you came to live to Southern Spain (the Andalusian region), probably you'll be hearing that word a lot, depending on the city you are living in. You may hear it more often in Sevilla, but you can also hear it in Cádiz, Málaga and other places.
The words illo, illa are just shortened forms of chiquillo and chiquilla:
Del dim. de chico.
- adj. niño. U. t. c. s.
- adj. muchacho. U. t. c. s.
So as you see, chiquillo means 'little boy' and its feminine form chiquilla means 'little girl'. The word chiquillo can be used as a vocative to call any little boy in the street, although it may sound quite outdated:
Chiquillo, ¿podrías decirme cómo se llega a la iglesia?
Hey boy, could you tell the way to go to the church?
The thing is, that word was too long to be used in quick conversations, so it was shortened to quillo, but in doing so it lost its original meaning and started to be used to call any person in a colloquial way, or just to give emphasis to the sentence you are about to say:
Quillo, que me tengo que ir.
Hey man, I gotta go.
In this case it would just mean 'hey' or 'hey man'. Note that the use of this word is quite colloquial and therefore should not be used in formal contexts, only in casual conversations.
The next step was to shorten the word even more, so it ended up being just illo, a word that is already registered in 1951 in the Vocabulario andaluz by author Alcalá Venceslada, along with the following example:
¡Illo! Tu padre, que vengas.
Hey! You father wants you to come.
The word illo can be used repeatedly for even more emphasis. The more it is repeated the more urgency there is:
¡Illo illo illo!
(Depending on the context it may mean from 'Quick, come and see this' to 'Are you crazy? What are you doing?'.)
Finally, note also that illo can be used as a 'verbal tic' word (or embolalia) with no meaning at all, just something a person adds to their discourse as a custom. I once heard someone having this conversation on the phone:
—Illo, ¿qué pasa, illo?
"Hey, what's up, man?"
those are diminutive suffixes, a word or part of a word that expresses the fact that something is small, often used either to show affection or to suggest something or someone is not important. Part of this definition is from the Cambridge dictionary, and it is right as it's defined. When we call someone by his/her name and we add the suffix illo or illa we are treating this person with any of these feelings above.