The term is a generic one, not specific to Mormonism. According to the Wikipedia article[1] (albeit from an uncited source), there are references to it from the year 567.
Mormons are the best known example of it, but many Baptist, Pentecostal and Brethren churches do the same thing. In all of those cases, where it happens, I believe that 10% is the standard figure.
The word tithe means tenth, and it is the biblical standard of giving - a tenth of your income. However, it's not related at all to tipping a waitress a portion of your dinner bill.
Religious people that write things like that prefer rhetoric to reason. It's in the same class of statements as "no monkey in my family tree." Sounds like you've made a point but you have only made a sentence.
How did Mormons come into this discussion? To tithe means to pay one tenth and always has. A "tithe" comes from the saxon "teoþa" which means "tenth". Plenty of sects tithe.
Mormons are only unique in this respect in just how seriously they take tithing and the lengths that they go to in order to ensure that it is being done properly. In most other Christian-based religions tithing is a more personal matter.
