In 1987, a woman has complications while giving birth. The woman's husband prays to his native deity that if she delivers his baby successfully, he would name the baby with the name of the deity. The baby is born without any problems and as per the wish, they name the baby, Kunjithapadham (Sivakarthikeyan).
As a boy, Kunjithapadham faces many problems and embarrassments due to his name. He decides to change his name. But his mother falls ill and he prays to god that he would never again wish to change his name.
Years later, Kunjithapadham's mother dies. His friend Peter (Sathish) advises him to change his name in order to have a change in his life. After meeting an astrologer (Manobala), he renames himself "Harish". Luck starts to him from that day onwards. He falls in love with Geetha (Priya Anand) and succeeds in winning her love. He later gets a job and life goes smoothly for him. One day, his lottery ticket hits victory and he must cash it in for a television as a prize. But, the lottery has registered his name as 'Kunjithapadham'. He makes up the drama with Peter and gets the television, but later faces problems and Geetha finds out his true name. Geetha berates Harish for lying to her about his name and that he needs to succeed something in life in order to win her heart.
Harish decides to participate in Chennai Marathon 2012 to achieve something in life. He meets with a trainer (Jayaprakash) who takes him to his former student Valli (Nandita) who had quit athletics. She agrees to train Harish and later, Harish sees her crying in the terrace with a photo of her dead father. Harish asks her to tell her past.
Valli was a naturally talented athlete from her young days. Her father (Sharath Lohitashwa) supported her talent and spoke with many men to get her past many tournaments. She got into State level tournament where she beat the rookie of the corrupt coach Raja Singh (Ravi Prakash). Infuriated, Raja Singh accused Valli of failing a gender verification test. The board punished Valli and stopped her from participating. Heartbroken, Valli's father died of a heart attack.
Hearing this flashback, Harish is moved and decides to win the marathon. Geetha also urges him to win it for the sake of Valli. During the marathon, Harish faces stiff competition from another one of Raja's rookies but eventually wins the race and publicly reveals Valli's innocence. Raja Singh is arrested, and Valli resumes athletics.
Harish later opens and runs a training academy under his original name. A man named Dinakaran (Attakathi Dinesh), acting on Harish's advice, proposes his love to Valli, and she accepts.
Dhanush signed up TV star Sivakarthikeyan in his maiden production venture. Priya Anand was signed up as heroine. She plays a fun character. The film's photo shoot involving Siva Karthikeyan and Priya Anand happened at the Set Fire Studios, Chennai on 7 Jun 2012.
It was reported that Dhansika of Aravaan fame was cast as the second heroine.Soon after Dhansikha's exit, the role was given to Vasundhara Das but Nandita of Attakathi has got the role. She plays the role of an athlete. Velraj of Polladhavan fame will handle the camera. Anu Parthasarathy is the stylist. Priya Anand revealed, that Ethir Neechal is a city-based story without cheap comedy, vulgar dialogues or inappropriate scenes.
The team begun shooting for the film on 23 Jul 2012. Balu Mahendra took the first shot. Dhanush and Nayanthara will be seen in a special appearance, dancing together in the Kuthu folk dance number Sathiyama Nee Enakku, with Nayanthara designing costumes for herself. The song was shot in Nagercoil at a Punjabi dhabha restaurant. A post-production press meeting was held on 24 April.
Anirudh Ravichander composed the music for this film; the soundtrack features six tracks that belonged to varied genres. The audio rights was brought by Sony Music.
Musicperk gave 8 out of 10 starts saying that "Anirudh seals this year". Behindwoods rated 3.5 of 5 saying, "The album does well to consolidate Anirudh's sensational debut "Anirudh is the real EDM artist . He is the first to bring original EDM music....Wasim - music engineer
The distribution rights of the film were secured by Vendhar Movies. The satellite rights of the film were purchased by STAR Vijay. The film was given a "U" certificate by the Indian Censor Board and is expected to release on 1 May 2013. The censors hinted, that the film would be wholesome family entertainer. The film released in 300 screens across Tamil Nadu. The theatrical trailer for Ethir Neechal was released on 13 April 2013. The film was released on 1 May with Soodhu Kavvum and Moondru Per Moondru Kaadhal and received highly positive reviews.]
The film opened 80 – 90% occupancy on first day collected ₹ 4 crore.The film total collection is ₹ 30+ crore.
Ethir Neechal received generally positive reviews, Behindwoods wrote:"just being a mindless romantic comedy, it also makes some valid points about the state of poor athletes in the country". Hindu wrote:"Sivakarthikeyan looks like he’s getting there — he’s not yet a star, at least in the leading-man sense,[sic] he gets a feature-length platform to display his comic chops". Indian Express wrote:"Ethir Neechal is a mild passable entertainer".