The First Thing That Everyone Remembers on Hearing the Name Avvaiyar Is Aathichudi. Aathichudi

The first thing that everyone remembers on hearing the name Avvaiyar is Aathichudi. Aathichudi is said to have been written by the later Avvaiyar. Aathichudi stands as a crown for tha works of Avvaiyar. Its simplicity and the moral values it inculcates has a wide acceptance among people. It is so simple that is even taught to kids just out of kindergarten, and even used by people as quotes during their ordinary day to day talks or speeches.
Aathichudi has 109 verses explaining the morals. The beauty is that it is organized in such a way that each verse is in the order of the vowels (Uyir Ezhuthu), consonants (Mei Ezhuthu) of the Tamil alphabets and the combinant alphabets (Uyir Mei Ezhuthu).
அறம் செய விரும்பு
Aram seyya virumbu
Desire doing righteous deeds
ஆறுவது சினம்
Aaruvadhu Sinam
Anger is to be controlled
இயல்வது கரவேல்
Iyalvadhu Karavael
Help others in whatever ways you can

ஈவது விலக்கேல்
Eevadhu Vilakkael
Never prevent others from providing charity

உடையது விளம்பேல்
Udaiyadhu Vilambael
Never proclaim/boast what you have

ஊக்கமது கைவிடேல்
Ookamadhu Kaividael
Never give up the confidence and hope

எண் எழுத்து இகழேல்
Enn Ezhuthu Egazhael
Never despise learning

ஏற்பது இகழ்ச்சி
Yaerpadhu Igazhchi
Accepting alms (begging) is despicable

ஐயமிட்டு உண்
Ayyamittu Unn
Share your food with the needy, before you eat

ஒப்புர வொழுகு
Oppuravu Ozhugu
Act virtuously

ஓதுவது ஒழியேல்
Odhuvadhu Ozhiyael
Never stop learning

ஒளவியம் பேசேல்
Ouviyyam Paesael
Never gossip about others

அஃகஞ் சுருக்கேல்
Akkam Surukael
Never cheat on quantity of items you sell

The name Aathichudi is because of the head verse is in praise of Lord Shiva and Lord Ganapathy, who is adorned with the Aathi flowers.

ஆத்திசூடி அமர்ந்த தேவனை
ஏத்தி ஏத்தி தொழுவோமே
Aathichudi Amarndha Devanai
Yaethi Yaethi thozuvomae

meaning, we will praise the The God (Lord Vinayaka) who sits in the lap of the Lord (Lord Shiva) who wears the Aathi flowers
The simplicity of these verses are not only easy to comprehend but also easy to remember. Very easy for learning kids, that they remember through out their life.
Another work, the Kondrai vendhan, is also by the later Avvaiyar, which is similar to the Aathichudi in many respects. The same one-liner style, along with the order of the alphabets makes it easy to read and remember too. This is praise of Lord Shiva, who is adorned with the Kondrai flowers, and Lord Vinayaka. Usually all Tamil poems being with a song that is in praise of the poet's favourite God. This verse is called the Kadavul Vaazhthu. Now, the verses from Kondrai Vendhan.

கொன்றை வேந்தன் செல்வன் அடியினை
என்றும் ஏத்தி தொழுவோம் யாமே
Kondrai Vendhan Selvan Adiyinai
Endrum Yaethi Thozhuvom Yaamae

We will ever worship and praise the Son (Lord Vinayaka) of the Lord (Lord Shiva) who wears the Kondrai flowers.

அன்னையும் பிதாவும் முன்னறி தெய்வம்
Annaiyum Pidhavum Munnari Dheivam
The mother and the father are the Gods to be realised first

ஆலயம் சென்றடல் சாலவும் நன்று
Aalayam Sendridal Saalavum Nandru
It is good and noble to worship the God in temples

இல்லறம் அல்லது நல்லறம் அன்று
Illaram Alladhu Nallaram Andru
It is ignoble to not follow a peaceful marriage

ஈயார் தேட்டை தீயார் கொள்வர்
Eeyaar Thaetai Theeyaar Kollvar
The belongings of the miserly will be plundered by the evil-minded

உண்டி சுருங்குதல் பெண்டிருக்கு அழகு
Undi Surungudhal Pendirukku Azhagu
Reducing the quantity of food intake, by women is good for them

ஊருடன் பகைக்கின் வேருடன் கெடும்
Oorudan Pagaikkin Verudan Kedum
Hostility with the society/country will destroy everything one has right from the root

எண்ணும் எழுத்தும் கண்ணென தகும்
Ennum Ezhuthum Kannena Thagum
Education and knowledge is like the eye for everyone

ஏவா மக்கள் மூவா மருந்து
Yaeva Makkal Moova Marundhu
Children who do the right things without the parents' guidance are like curative medicine

ஐயம் புகினும் செய்வன செய்
Aiyyam Puginum Seivana Sei
Even under impecuniousness do your duties

ஒருவனை பற்றி ஓரகத்து இரு
Oruvanai Pattri Oragathu Iru
Marry one and be loyal the spouse

ஓதலின் நன்றே வேதியர்க்கு ஒழுக்கம்
Odhalin Nandrae Vedhiyarkku Ozhukkam
Discipline is more important to a priest than uttering the sacred hymns

ஔவியம் பேசுதல் ஆக்கத்திற்கு அழிவு
Auviyam Pesudhal Aakkathirkku Azhivu
Gossiping is destructive to one's fame

அஃகமும் காசும் சிக்கென தேடு
Akkamum Kaasum Sikkena Thaedu
Earn cultivation lands and the money soon in your life