Thanks to Aviyal Expert Purni’s dad, who got me the meaning of the opening lines of the song ‘TheeNdai‘ (Which is actually Kurunthogai as reader Pandya pointed out)

Here it goes

The context - The heroine is confiding her deepest feelings to her
friends in the absence of her lover who has gone out of station on
business or for war.

கன்றும் உண்ணாது, கலத்தினும் படாது,
நல் ஆன் தீம் பால் நிலத்து உக்கா அங்கு,
எனக்கும் ஆகாது, என்னைக்கும் உதவாது,
பசலை உணீஇயர் வேண்டும்-
திதலை அல்குல் என் மாமைக் கவினே

Line 1 - Kandrum Unnaadhu Kalathinum Padaadhu
Nal Aan Theem Paal Nilathu ukkaa Angu

When the cows milk is neither enjoyed by the calf nor consumed by
humans, but goes to waste on the Earth.

Line 3 - Pasalai Uni Iyar Vendum
Pasalai is the vacant feeling expressed in one’s looks and is
attributed as a disease. The cow is said to have a vacant look in its
eyes when its milk goes waste.

Line 2 and 4 - The Heroine tells her friends that she is now suffering
from this Pasalai disease in the absence of her beloved. She pines for
her lover saying that her youth will go waste and will not be used
till his return. She tells her friends that she is destined to suffer
this disease till he returns. She asks her friends how they can help
her in such a state. She tells them that their company and soothing
words will keep her alive.

Super :)