His mother Anjana named him Sundara after birth. Hanuman was the name given after his jaw grew out to be a disfigured one. Hanuma means ‘jaw’ or ‘chin’. Anjaneya was the name given after his mother Anjana.
Parasara Samhita, the only authentic book on Hanuman with complete details, mentions few slokas where Sundara (Hanuman) as an infant asks for food on a new moon day. His mother Anjana asks him to eat any fruit. He sees rising Sun, assumes it to be a fruit and gets closer. Indra hits him with Vajrayudha on cheek and it swells.
Since his cheek/jaw (hanuma) was swollen/disfigured, he was named Hanuman.
This story of Hanuman trying to swallow SUN is actually Vrishakapi (Orion or Mrigasirsha constellation) journey from Winter Solstice to Vernal Equinox, which appears like as if Orion constellation is following the Sun.
As Orion appears like a human figure (hunter), it can be imagined like a man chasing a fruit.
This period (December – March) is when there are no rains in Northern Hemisphere (above the equator). Majority of human population live in this zone, they experience winter and no rainfall.
Indra is the God associated with Rain and he is not worshipped during this period. This is the reason why Vrishakapi is a competitor to Indra.
Infact, one of the Orion’s brightest stars Betelgeuse (Alpha Orionis) is a Red supergiant and is so big that, Sun appears like a small dot in front of it.
When Sun appears to travel along with Ascendant (between December-March every year), Orion will be appearing to travel towards Sun at the same pace.
When this big Betelguese, along with other constellations in Orion appears to travel towards a tiny Sun, obviously Sun appears like a tiny red fruit.
This entire astronomical event was etched into a folklore story in Parasara Samhita and later into Hanuman Chalisa by Tulsidas.
Hanuman was born with a normal human face but with disfigured jaw, which was explained by rishis as effect of his past life act of clash with Indra.
Valmiki used the named Hanuma throughout Ramyana except for Sundarakanda, which he named after Sundara, instead of Hanuman Kanda.
Sundara Kanda is the only chapter of the Ramayana in which the principal protagonist is not Rama, but Hanuma.
The entire episode lasted for 24 hours and is all about heroics of Hanuman, who flew over sea, searched through entire Lanka, found and talked to Seetha, fought and killed Ravana’s army, got wilfully caught by Indrajit, set lanka on fire and returned by crossing the sea again.
Through out this journey, he neither rested nor ate food.
Sundara Kanda is the best example of how focused one must be to achieve a goal.
It is advised by scholars to recite Sundara Kanda to overcome hurdles in daily life, but the real intention is to make us understand how focussed was Hanuman, rather than just reading it for namesake.
In Sanskrit version of Ramayana, most names end with vowels, especially ‘a’.
Hindi is a later created or derived language from Khariboli, Prakrit, Apabhramsa and Persian languages.
They spell Rama as Ram, Sundara as Sundar, Siva as Shiva (without differentiating between सा, श, ष while pronouncing).
Few people assume that due to beautiful (Sundar) description of Lanka and Ashoka Vatika, it is called Sundara Kanda, which is wrong !
Also, in few Indian states, Hanuman Jayanti (Janmotsav) is wrongly celebrated in April on Chaitra Pournami (full moon day).
Sundara Kanda clearly states that Hanuman found Seetha under a tree in Asoka Vatika on early Tuesday morning, which was Chaitra Pournami.
On this day, he killed much of Ravana’s army and burnt more than half of Lanka single handedly.
This should be celebrated as ‘Hanumad Vijayam’ (Hanuman’s victory).
Parasara Samhita clearly states that Hanuman was born on Anjanadri Hill (one of seven hills in Tirunala), on a Saturday, Krishna Dasami (10th lunar day after fullmoon) in Vaisakha Maasam (usually comes in late May every year), with Moon in Poorvabhadrapada nakshatra.
Anjana did penance for Siva and was blessed with a child, who was one of the Rudra (Eka Pada Rudra).
She named the child Sundara, as it is one of the names (forms) of Siva.
When Siva along with all the gods went to ask Parvati’s hand as bride, her parents asked him to present appear in a more beautiful form for marriage, than a hermit with skull garland.
Siva changed his attire for marriage and than new look was called Sundara.
In Meenakshi Kalyanam episode too, Siva appeared as Sundareswarar or by the name Sundara Pandyan to marry her and they both ruled Madurai for many years.