Product name similarities.

The below does not constitute legal advice, does not form an attorney-client relationship, and should not be relied upon to take or refrain from taking any action.

When naming a product the owner must consider whether its potential names would LIKELY cause consumers to mistakenly believe that someone else either produces the product or sponsors, endorses, or is associated with the product due to the other person's similar product name or other trademark.

A computer game similar to Yahtzee and named Yahtzoo is, for my money, likely to cause that consumer confusion.

You should come up with five or so potential names (considering the rule articulated above), list them by preference, and then have a trademark attorney go down the list and opine on whether your use would be lawful -- the first one that clears that hurdle is your brand name.

Generally, if you're trying to capitalize off an established mark by using something similar, you're not in the best position and are risking. As Mr Ballard stated, you should run possible names by a trademark attorney to avoid problems down the road.

Yes, if you want to use a name similar to that of of a known product precisely to trade on the fame of that product, chances are, you're infringing. The legal standard is consumer confusion, and it sounds like you're deliberately trying to tap into the consumers that already know this famous game to further your computer game. Trademark law is quite complicated, so you're best off hiring a qualified trademark lawyer and performing a professional search prior to choosing a name for your product.

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.