I assume you mean dimensions M, L, and T as used in mechanics, ie mass, length, and time. See Wikipedia entry for 'Dimensional analysis'. There doesn't seem to be one name for who thought of the idea, it probably evolved through many people from Newton on.
Nobody discovered them, they were always there. But mathematicians round 1900 started to work with them and call them dimensions.
Nobody knows who truly came up with the original idea, and it was likely that many had the same idea, since people around the world began selling bottles of water from special springs that were said to be medicinal.
Charles Darwin came up with the idea of natural selection during the voyage of the Beagle between 1831 and 1836. His book On the Origin of Species was published on November 24th, 1859.Another scientist named Alfred Russel Wallace also came up with the idea of natural selection, independently from Darwin and around the same time.
Charles Darwin came up with the Idea of Evolution by means of Natural Selection, this eventually became a scientific theory.
who came up with the idea of NAFTA
The founding fathers came up with the idea of independence. They adopted the idea from the French people during the French Revolution,
The Mac Cosmetics company came up with the idea for MAC powder. It is unclear exactly which employee came up with the idea but it was probably a collaboration between several departments there.
The company Ganz did, but the individual who came up with the idea is not named.
who came up with the ancient olympics
I am pretty sure masashi kishimoto came up with the idea because he did draw them.
It came up to sell Sticky Tape.
no one actually came up with it but ptolomy came up with the first model of it or you could say aristotle