I don't care about the trademarks, but as a Brit 'Legos' always sounds wrong, like "I'm playing with my sheeps".
- Math is short for mathematics, not for mathematic, which isn't a word (try looking up 'mathematic' sometime).
- Maths is also short for mathematics.
Was mathematics once referred to as "the mathematical arts" or something?
(A similar way to appear very uncool is to walk into a record shop and proclaim, "look at all these vinyls!")
Etymologically it is a plural suffix, but in modern English it is singular.
A history of math vs maths: http://m.youtube.com/watch?v=SbZCECvoaTA