Company A: as an example operates under Fluffy Apples... I would like to setup FluffyOranges As you can see, the only terms in common are "fluffy" however we sell the same product.... From what I can tell, companyA does not have the term "fluffy" trademarked, however, companyC has a trademark on "fluffy" (completely different products...) Legally speaking, would I have any issues from CompanyA by using FluffyOranges since they do not own the term "Fluffy"? Would they still have any case by saying we are selling the same product or that I am trying to confuse their brand...
Probably not. Since your examples probably isn't close enough to the real names to be really useful, let's just go with the fact that they do not have a registered trademark. If you wanna be sure, register your name as a trademark.
They do have a trademark for their actual brand... The examples above was product examples, but the words they are using for their product are generic in nature, not that it matters, I have run across general/generic words being trademarked, but in this case, I think another company owns the trademark, different products...
If A and B were both selling widgets (brand and product names exclude the word "fluffy") and A had a store (online or bricks) using the word "fluffy" and B sets up with it then B can expect hell to rain down. Whether it would stand up in court depends on where you are, precedent etc but B could spend a lot of money defending their right to use the word. If B and C were in different industries C's trademark won't apply as (in NZ anyway) a trademark is applied to a business category. Therefore my electronic appliance called ABC and packaged in Cadbury purple doesn't infringe on the trademark ABC in clothing/textiles or on Cadbury's use of purple with food.
when you file a trademark, you have to specify the category of items or services you will sell. they don't apply to anything you don't select. i know a pizza store by me called Ferrari's and another named after the Sopranos... nothing eith can do (except maybe if the logo looks the same)
@sarahk has made the most salient point here about spending a lot of money. The REAL question to ask is do you have pockets deep enough to defend the company's name when the competitor inevitably comes after you. A lot of these (perhaps most) copyright cases never actually make it to a verdict because one of the litigants runs out of money long before the legal process is over and that leads to a settlement in favor of the company with the most money to back up their "trademark." If you are asking questions about the legality of a trademark, you are on the path to a long and expensive legal battle once you get on the other company's radar screen. So, what can happen is that you work hard for months or years building a brand, establishing a customer base and then, when you are starting to gain traction and visibility, the "infringed" company starts an expensive and very distracting legal battle. I have seen this happen time and again and I often wonder why people would work so hard on a business that has a big potential vulnerability.
This is the last place to get legal advise in my opinion. If you're seriously considering this then I would suggest contacting a local attorney. A 5 minute phone call can answer this without leaving you with any doubts/worries.