Why does Tony call his daughter Maguna?

This is just a nickname of Morgan for Tony Stark.

There is nothing else significance to this name. Tony was playing with her that's when he calls her Maguna. So, we can assume it's just a cute nickname.

Actually he calls her Maguna twice-once outside when trying to find her by the tent, and again when he tells her the “horrible story”...”Once upon a time Maguna went to bed...the end”.

It seems like a pet name given to her, much the same way many fathers have pet names for their daughters. It also could’ve been how Morgan pronounced her name when she was first learning to talk-unfortunately we never got to see that darling child during her toddler years.

I think it's because they want to make the world of the MCU more relatable to our lives and to make Tony feel like an actual father. Scott Lang, for example, calls his daughter "Peanut" all the time, throughout both the Ant-Man films and Infinity War, so I honestly think it's to make the characters feel more grounded in their universe. Even with its comics, Marvel has always tried to make their superheroes have human-like qualities, like how Peter Parker is always nervous or anxious. It's a nice touch to make you feel like you're a part of their world.

I've got two proposals which are probably very intertwined:

1. Maguna is a town in India, North of Ahmedabad (North-West India): In Spiderman: Homecoming Tony Stark rescues Spiderman from the bottom of a lake. Later, they talk to each other and Spiderman at some point realizes that Stark isn't in the suit. Instead he's remotely controlling it from some place in India. It happens to be that there is a town called Maguna in North-West India. Morgan might have been conceived there. Although I must admit that I haven't found any time-related connections: Homecoming took place in 2016, Infinity War in 2018.

2. Maguna is Marathi (an Indo-Germanic language still spoked by 83 million people in India, especially in the state of Maharashtra) and can be translated to "afterwards", i. e. his life after Iron Man / Avengers. This makes sense when considering that scene from proposal 1). In this Quora-post someone assumes Stark to be at a friend's or an associate's wedding. He also includes a picture from Age of Ultron where there was an obviously Indian man at the party (right before Ultron introduced himself / itself). Others on that same Quora-post suggested he was there to "center himself". This idea stems from the original script in which Stark tells Spiderman he was in India to center himself. He might have learned some of the language while being there.

Anyway, (fortunately for my arguments), Maguna has been part of the former Maratha Empire and Mahatma Gandhi founded his Ashram in Ahmedabad. So, both of my suggestions might be valid or even are valid in conjunction. After Captain Marvel rescued Stark he might have taken Ms. Potts to Maguna, Ahmedabad or some place in Maharashtra to center himself once more, and to conceive

Maguna - his life after Iron Man

fyi @ all those who say that Maguna is just a nickname that doesn't mean anything: You are wrong. Try to write a story, and you will understand very fast that there is nothing like "doesn't mean anything" in an author's mind when composing a tale, especially one of this spectacularity.

Alright, this was bothering me as well. We will never know for sure until the bros confirm why they chose “Maguna” as a precious nickname for Morgan H Stark, but here is my best guess.

Tony is intelligent, as is Pepper, and we can assume if Tony calls Morgan “Maguna” there is a fair chance Pepper also called her daughter this pet name, as many parents do this. I’d like to think they took these as root words and combined them for a pretty nickname. The name “Mag” means pearl, and the name “Una” means the personification of truth, beauty, and UNITY. I’d like to think that once Tony found out about the confirmed pregnancy of Morgan, since he already knew because he has visions, that he decided this baby would be his “stone”. He is protective of Morgan at all costs. He immediately turns down Steve because he refuses to jeopardize losing Morgan. I also believe ultimately having Morgan brought Tony to a new level of peace from the pain he was enduring for YEARS after Civil War and she became the unity the Avengers needed to bring everyone back. She is even mentioned when Tony offers the peace offering of Cap’s shield.

It’s also possible that Maguna is a nickname relevant to his mother (or of course pepper’s family) but I haven’t looked into that at all. I think about that because the H in Morgan H Stark likely stands for Howard, so it would make sense that his nickname for his daughter would be related to his mother because we know how much he loves his mom.

Maguna means Humor, forgiveness and shrewdness. An apt nickname for Tony's daughter. Simple as that.