The goddess Îðunn and her basket of apples is a riddle not solved by any scholars. Her name if often translated as «the rejuvenator» or «ever young», however this is not an actual translation of her name, but rather an interpretation of what she does. Her Norse name Îðunn, from proto-Nordic *Îþund, from PIE *Eduno, translates as «laborious», «industrious», «who wants to work», and she is known from other parts of Europe as Proserpina (Rome), Epona (Gaul), Kostroma (Scythia) and Persephone (Greece).
Just like her husband, Baldr, is in Scandinavia also known as Bragi, she is also known as Nanna, which happens to mean almost the same as the name Îðunn; Norse Nanna from proto-Nordic *Nanþan, which translates as «zeal», «resourceful», «eager to work» and «rush».
When you see this in the light og how they selected their May Queens you start to understand what she is and why she is equipped with apples of eternal youth. As we can recall the girls were made eligible for the role of May Queen based on amongst other things their willingness to work, their eagerness to work, their industriousness, and so forth.
Baldr («ball») is known as Bragi («the winner», «the best»), because he is the winner of the May contests. His wife is then naturally Îðunn/Nanna, the most industrious of the young girls, selected by lottery or when Baldr handed her an apple. As we known from the myth about Paris she was also known as Freyja/Aphrodite, but don’t let this confuse you; they are just different names for the same goddess.
Now, Îðunn is not known to have been given an apple, but to hand out apples herself, to all the other deities, and this is what kept them eternally young. After she was given an apple, or picked by lottery, she – the lovely young May Queen, the embodiment of the youthful health and beauty of nature – was tasked with appointing new gods and goddesses every year, whenever a god or a goddess was no longer young, healthy and beautiful enough to be a god or a goddess. The gods were real human beings, who had been selected to become this or that deity, and the role of this or that deity was given to them by the May Queen, as she handed them an apple to appoint them «god» or «goddess». This is how her apples could keep the deities eternally young! The no longer young, healthy and beautiful deities returned to being normal human beings, and former normal human beings became deities as they received an apple each from the May Queen, Îðunn.
In each society, in each tribe, there was only one Ôðinn, one Þôrr, et cetera, and it was naturally considered a great honour to become such a deity – and each married man and woman became a Freyr and Freyja as well. Their priests and priestesses married the members of their “congregations”, in sacred marriages, and they came under the protection of their deities. Each year they held contests amongst themselves to see which one of them would be the best to be the god or the goddess. The winner was given an apple by Îðunn. The contests favoured health, youth and beauty, so those lacking this were not made deities, or were not allowed to continue as deities. The deities were forever young, beautiful and healthy. They were always the best amongst them.
The demi-deities, the heroes and heroines described in Greek mythology, were the men and women already married to a deity (so they were demi-deities), but who had to go through rigorous tests to be allowed to become one themselves (i. e. and to take over the role of the deity from another person).
The May King was the real King of the tribe, and the May Queen the real Queen, and originally they represented all the gods and all the goddesses. The King was the Sky God, the Queen the Earth Goddess. With time this changed, and different faces of the one Sky God and the one Earth Goddess were individually impersonated. The mighty Sky God, Norse Tyr, from younger proto-Nordic *TîwaR, from older proto-Nordic *Tîwaz, from PIE *Diwos, is better known by us from Old Latin Divus and Latin Deus. Or from Sanskrit Dêva, Welsh Duw, Gaulish «Great Father», Scythian Rod/Div, Lithuanian Diêvas, Greek Zevs/Uranos et cetera. Therefore we learn in Scandinavia that Tyr was once the King of the gods, but in the Viking Age he had been «replaced» by Ôðinn. He wasn’t really; it was just that Ôðinnic part of him that became the most important in society at that troublesome time.
Some European tribes divided the powers of Tyr up into many, others only into a few, separate gods. The same applied to the Earth Goddess; Norse Jörð, proto-Nordic Erþo, Greek Demeter/Hera/Kybele, Scythian Matushka/Vesna, Western European Danu-Ana/«The Lady», Roman Juno, et cetera. When different European tribes later came into contact with each other the often identical deities became incorporated into often both the tribes’ pantheon because they called them by different names, and both tribes all of a sudden had e. g. two Moon Goddesses. Other times a deity could disappear from a pantheon. None of this really mattered though; all the deities were just different faces of the same concept of a positive spiritual force in our universe that is both masculine and feminine. The different faces of this force is found in the Sun and the Moon, the stars and constellations, in the reflection of light from the planets and in everything else in our world too.