I will first give the direct meaning of this pasuram and then discuss the commentaries of early Acharyas.
கண்ணினுண் சிறுத்தாம்பினால் கட்டுண்ணப்
பண்ணிய பெருமாயன் என்னப்பனில்
நண்ணித் தென்குருகூர் நம்பி என்றக்கால்
அண்ணிக்கும் அமுது ஊறும் என் நாவுக்கே.
In brief, in this verse Madhurakavi says he is forsaking Krishna for Swami Nammazhvar, the one whose name when said is sweet to the tongue and produces a groundswell of ambrosia.
கண்ணினுண் சிறுத்தாம்பு = A rope made from small pieces of ropes bound together with small knots
நண்ணி = leaving, i.e., என் அப்பனில் நண்ணி = leaving my lord Sri Krishna
தென்குருகூர் = Present day Azhvar Thirunagari, native place of Swami Nammazhvar
நம்பி = பரிபூர்ணன்; female பரிபூர்ணி is நங்கை
அண்ணிக்கும் = தித்திக்கும், sweet taste (Not sister-in-law)
The major themes the commentators focus on in this verse are (i) கட்டுண்ணப் பண்ணிய which refers to the fact Lord Sri Krishna allowed himself to be bound by Yesoda, and (ii) என் அப்பனில் நண்ணி which refers to the rejection of Lord Sri Krishna in favor of Swami Nammazhvar.
It is absolutely amazing to see how much meaning the commentators saw in this little phrase "கட்டுண்ணப் பண்ணிய".
First, they suggest that it was Krishna's wish to get bound, but wanted to have some fun. So, before embarking on his butter thievery Kannan took all the ropes in the house and cut them to small pieces. Then he embarked on his mission of larceny. The commentators marvel at this little scheme.
It is a wonder, they say, that Sarveshwaran decided to descend to this earth as a little helpless child. Even more wondrous is the fact he became hungry, that too for mere butter. A further wonderment is he decided to steal some butter. To top that, he made a mess of it, by smearing the butter all over his face and body. The height of all this was to deny he did any butter stealing when he was confronted by Yesoda.
Why did he do all this, the commentators say because he wanted to enjoy the banter with his devotees. When an ordinary person steals anything he/she will be put in jail, but when the one who owns everything in this world and the other, resorts to stealing something that belongs to him in the first place, it is what legends are made of.
Now, having caught Kannan red-handed, Yesoda decides to bind him to the millstone. But all the ropes are cut into small pieces. So she binds them all with knots to make a big rope. This is the reason Madurakavi says it is கண்ணினுண் சிறுத்தாம்பு, a rope made of lots of small knots.
But, when she tries to bind him with this makeshift rope to the millstone, the rope is not long enough. Seeing Yesoda struggling to bind him, Kannan shrinks his body just enough to free her from her predicament. This is the purport of the choice of term கட்டுண்ணப்பண்ணிய, instead of கட்டப்பட்ட.
Now, not realizing that Kannan allowed her to bind him, Yesoda is triumphant that she was able to bind her mischievous little son and challenges Kannan to free himself if he can, and goes about her business.
Now, Krishna stays bound, on his own accord. The all powerful, the one who can cut even the worst of all bondage, namely samsara, is powerless and stays bound by a small little makeshift rope, made out of many flimsy knots, by a little lady Yesoda, whose very sustenance is provided by him. The one who binds all jeevas into samsara is now bound by a mere jeeva.
It is said that only the one who binds can provide release from bondage. Kannan binds all jeevas into samsara, and only Kannan can provide release. Kannan now wishes to follow the same rule. Since Yesoda is the one who bound him, he awaits Yesoda to come and release him. This gives him immense pleasure. Anyone who contemplates upon this divine bondage, the commentators say, will get release from their bondage to samsara.
The commentators compare this bondage to what one calls பேராண்மை in Tamil. To wage wars and defeat enemies is only ஆண்மை. But, to stand defeated by the one you love and get bound by her is பேராண்மை. The commentators explain this with a story. A great king set out to track down and defeat an enemy. The queen says he should get the enemy alive and bring him in before sunset. The king accepts the challenge and agrees to suffer any punishment at her hands if he fails.
After all his efforts, the king succeeds in capturing the enemy alive and brings him home, but he is late, it is two hours after sunset. He enters his andhappuram and not seen for a long time. The impatient general waiting outside dares to enter to see what is going on. He sees the king bound to a pillar by a strand of flowers from the queen's head. Amazed, the general asks what is the deal. The king answers, conquering enemies is only ஆண்மை, but submitting to the punishment of the one you love is பேராண்மை. Likewise, Kannan, who is Iswara himself, who could free himself from anything, stood helplessly bound by a little woman who is part of his own creation, all for love.
This is seen as the epitome of Iswara's love for jeevas. When Nammazhvar sang about this super Sowsheelyam, the nature of a great person to humble himself in front of his love, like Rama embracing Guha, and Anjeneya, the Azhvar went into a stupor for six straight months. Here is that pasuram from Thiruvay mozhi 1.3.1:
பத்துடை அடியவர்க்கு எளியவன், பிரர்களுக்கு அரியபத்துடை = one possessed of bhakti
வித்தகன், மலர் மகள் பவிரும்பும் நம் அரும்பெறல் அடிகள்
மத்துறு கடை வெண்ணை, களவினில் உரவிடை ஆப்புண்டு
எத்திறம் உரலினோடு இணைந்திருந்து ஏங்கிய எளிவே!
அடியவர்க்கு எளியவன் = easily approachable to such Bhathas, this is called sowlabhyam
பிரர்களுக்கு அரிய வித்தகன் = but inscrutable to those without that kind of bhakti
மலர் மகள் பவிரும்பும் நம் அரும்பெறல் அடிகள் = our lord loved by Mahalakshmi
மத்துறு கடை வெண்ணை = butter churned by maththu
களவினில் = getting caught by stealing that butter
உரவிடை = in the chest
ஆப்புண்டு = getting bound
எத்திறம் = such a wondrous sight to see
உரலினோடு இணைந்திருந்து = the lord bound to the millstone
ஏங்கிய எளிவே! = meek humility
Lord Krishna, the one loved by Mahalakshmi residing in lotus flower, is ever so easy to approach for those with Bhakti, but is ever so distant to those bereft of it, look how simple he is, allowing himself to be bound to a millstone by getting caught steeling some measly butter. The very idea that Sarveshvaran is allowing himself to be dictated to by an illiterate cowherd woman was enough to send Swami nammazhvar into a trance for six months.
The commentators also cite a verse from Thirumangai Azhvar, from a set of verses in which a click of girls tease one of them (the Azhvar himself in nayaki bhavam) who is head over heals in love with Kannan. Here is the exchange between the silly little girls.
வண்னக் கருங்குழல் ஆய்ச்சியால் மொத்துண்டு
கண்ணிக் குறுங்கயிற்றால் கட்டுண்டான் காணேடீ,
கண்ணிக் குருங்கயிற்றால் கட்டுண்டான் ஆகிலும்
எண்ணற்கு அரியான் இமையோர்க்கும் சாழலே. 11. 5.5.
The first two lines is about the girls making fun of Kannan getting beaten and bound with a makeshift rope by a cowherd women. This is an illustration of the Lord's sowlabhyam, ease of befriending. The last two lines constitute the an answer to the mocking by the girl who is immersed in love for Kannan, the girl is Azhvar himself in Nayaki Bhavam, that proclaims Kannan's greatness.
Note the similarity of expression with Madhurakavi, both use the term கண்ணினுண் கயிறு. But, Thirumangai goes one step further and says he gets beaten by the rope, மொத்துண்டு. He also uses கட்டுண்டான், implying it was his wish and he allowed himself to be bound. The first girl makes fun at Kannan, look he got beaten by a cowherd woman with a rope. Then, the girl mad with love for Kannan, the Azhvar himself, answers, so what, even though he was bound by a simple cowherd woman, his greatness is beyond the comprehension of even the devas.
All this is to show how great is Madhurakavi's control of his senses, a true Shathrugnan, to leave the Lord oozing with humility for his devotees and seek out servitude for Swami nammazhvar. That is illustrated by the phrase, என்னப்பனில் நண்ணி, and that is for tomorrow.
p.s. I hope all the time I am spending on this is of some use to somebody!