What does isimo mean when used at the end of a person’s name?

Question

I have a close friend that says this when saying my name, and I find it very endearing. Just curious as to the exact meaning of it

Answer 1

-ísimo

Suffix. It is used to form the superlative degree of many adjectives, indicating "highly, extremely". Examples:
Alto → Altísimo
Grande → Grandísimo

_{Source wiktionary}

It is not used in proper names, except to make a joke whose meaning is to magnify the person.

---

There is a comic character from "Los padrinos mágicos", called Juanísimo Magnífico (Juan-ísimo). Perhaps your friend takes this character as a reference to say your name.

Answer 2

I imagine the superlative added to a name might be used to mean that the person in question is very much like him/herself on the occasion at issue. This would work especially after the verb "estar", for example:

(To a person called Pedro):

• Hoy estás Pedrísimo (= más Pedro que nunca).

If Pedro is handsome, "Pedrísimo" will mean "more handsome than ever".