The name Megatron was not first given to the evil robot leader of the Decepticons. No, in fact, the first appearance of that name in print predates the 1984 release of the Transformers toy line and cartoon series by 22 years.
It was, in fact, first a nickname given to Meg Murray by her father in A Wrinkle in Time, published in 1962. It appears to be simply an application of the Greek ending -τρον ‘instrument of’ to her name, playing off the word mega. So it would mean ‘huge device’ or ‘instrument of awesomeness’! Her father being a genius scientist, him deriving such a name makes sense.
(There’s a slight chance, based on scant and obscure internet evidence, that it’s a play off of magnetron or is its own sort of sealed tube used in “lighthouses and submarines“, being built from mega ‘great, big’ + electronic.)
It was Madeleine L’Engle then who was the one that coined the term, not designers at Hasbro and Takara.
And it’s likely they both arrived at it independently from different angles of ‘big awesome instrument/device’! But L’Engle was the first to do it by over two decades.
Limn 