*Lithsiummath(ematic)s abbreviated to math's, hence the apostrophe indicating there are missing letters, subsequently dropped as people couldn't be bothered to write the ' hence maths, unless you're 'murcian in which case you can't even be bothered to put the s on the end and wouldn't even know that in the correct form of English such things as ' exist to indicate there are missing letters.
Now, back to Lithium.