All three are basically descriptive of sounds that emanate from a distressed Palagattan. The beauty of Palagattan Tamizh is evident in these 3Ms__each one aptly contextualized for specific moments of distress.
'Mukkal' is Palagattan for the unsuppressable moan that comes from someone who is struggling in the loo. It basically describes the vocal suffering of one who is constipated. A typical usage would be: "Paavum akkum avan, kollai-le mukkindu irrukkan". "The poor guy is moaning in the loo". However, what needs to be noted is that constipation is implied as the sufferer's condition when the Palagattan statement is made. The English translation, sadly, does not do as much justice though.
'Muttal' is Palagattan for the painful moan that someone suffering from an asthmatic attack makes. An asthma attack leads to a condition called wheezing. This is what in Palagattan is called 'eiyuzhippu'. But Palagattans also have a poetic streak in them. So, they went further than the act of 'eiyuzhippu' (wheezing) and defined the moan that emanates at the end of each wheeze. Purists would understand 'muuchu muttarthu' as a phrase in Tamizh that means 'suffocating' or 'choking' or 'out of breath'. And since asthma is basically the condition when the lungs receive lesser oxygen, Palagattans borrowed and embellished the 'muttarthu' word. 'Muttal' is the noun to describe the action called 'muttarthu'. An elderly Palagattan could say: "Avan kitta chitha peshadikki irrukka chollu. Paaru, epidi muttarthu." "Just ask him to stay quiet and not talk too much. Look how bad his wheeze (and moan__sic!) is!!"
'Monaghal' is Palagattan for muttering under one's breath. Often when young Palagattan girls are asked by their mothers to clear the prayer (saami) room or draw the traditional motifs made of rice powder (an entire process called 'vaasal thelichu kolam podarathu') in the front yard of the house, they mutter under their breath. Sometimes, young Palagattan boys are asked to join in the prayers or take their grandparents to the doctor, while all they want to do is oogle at the girls in the neighborhood, and they too mutter under their breath. So, 'monaghal' is not just a sound or a metaphorical moan. But describes a series of incomprehensible words spoken__like the lingo of the zoozoos in the currently playing classic Vodafone ads. The Tamizh word for this is 'polambal'. A typical Palagattan usage would be: "Enna da, monagharai? Ni Monaghinathunaala unnam naan mashiyamatten, kettiya?" "Why are you muttering under your breath? Remember, your muttering protest is not going to make me give up or give in. Get that."
Perhaps, this blog, if it had been written earlier, could have given Danny Boyle a creative suggestion for his highly acclaimed SM. Instead of using The Three Musketeers from Alexander Dumas in his script, he could have possibly gone with the Palagattan 3M?