(Translation on request for AP)
Joseph, a law enforcement officer provides the emotional support to his wife Stella during the labor of their first child. He brings them home and takes care of his family. The lyrics of this beautiful lullaby suggests that it is being sung to the child, but I think it is also meant for Stella as he is seen taking care of her like a child in the scene.

To listen to the song, click play:

Poomuthole nee erinja vazhiyil njan mazha aayi peythedi
Aariraaram idaralle manimuthe kanmani
[Hey my precious girl, on the paths you burned (in pain), I drizzled down as (comforting) rain
Let my lullabies never falter, my darling child]
Maarathu urakkaan innolam thanal ellam veyil aayi kondedi
Maanatholam mazhavil aayi valarenam en mani
[To make you sleep on my chest in the shade, I took all the heat from the sun
As tall as the sky like a rainbow, you should grow my love]
Aazhi thiramaala pole kaathu ninne aelkkam
peelicheru thooval veeshi kaattil aadi neengaam
[Like the deep ocean’s (calm)tide, I’ll protect and keep you safe
Flapping your small feathery wings, swing and move in the breeze]
Kaniye, nee en kanavithal aayi nee vaa
Nidhiye, madiyil, puthu malar aayi vaa vaa
[Hey my fruit, please come in my dreams
Hey my treasure, on my lap, please come as a new flower]

Poomuthole nee erinja vazhiyil njan mazha aayi peythedi
Aariraaram idaralle manimuthe kanmani
[Hey my precious girl, on the paths you burned (in pain), I drizzled down as (comforting) rain
Let my lullabies never falter, my darling child]

Aarum kaana maettile thinkal neyyum koottile
eenakkuyil paadum paattin thaalam pakaraam
[On the never seen before meadows, in the nest weaved by moon
to the beats of the song bird’s music, I’ll (gently)tap you (to sleep)]
Perumani poovile thaen ozhukum novine
omal chiri noorum neerthi maarathu othukkam
[My little flower, all your sweet little pains
with a blooming cheerful smile, I’ll embrace]
Snehakaliyodam aeri nin theerathu ethum kaaval aayi
mohakothivaakku thooki nin chaarathu ethum omal aayi
[Embarking on the play-boat of love, I’ll reach your shores to keep you safe
Swinging words of affection, I’ll come near you sweetly]
Ennenum kanne nin koottu aayi
nenjil puchiri thookunna ponnomal poovu urangu
[I’ll always be with you, my precious
the one who smiles, my adorable flower, please sleep on my chest]

Poomuthole nee erinja vazhiyil njan mazha aayi peythedi
Aariraaram idaralle manimuthe kanmani
[Hey my precious girl, on the paths you burned (in pain), I drizzled down as (comforting) rain
Let my lullabies never falter, my darling child]
Maarathu urakkaan innolam thanal ellam veyil aayi kondedi
Maanatholam mazhavil aayi valarenam en mani
[To make you sleep on my chest in the shade, I took all the heat from the sun
As tall as the sky like a rainbow, you should grow my love]
Aazhi thiramaala pole kaathu ninne aelkkam
peelicheru thooval veeshi kaattil aadi neengaam
[Like the deep ocean’s (calm)tide, I’ll protect and keep you safe
Flapping your small feathery wings, swing and move in the breeze]
Kaniye, nee en kanavithal aayi nee vaa
Nidhiye, madiyil, puthu malar aayi vaa vaa
[Hey my fruit, please come in my dreams
Hey my treasure, on my lap, please come as a new flower]

+Image copyright to the original uploader.