George Carlin is gone. He was one of a few old-school comedians who managed to stay relevant with younger audiences despite the generation gap. The groundbreaking comedian died in California last night.

His blunt observational humor won him legions of fans and an occasional critic. He was no stranger to controversy. His signature routine, "7 Words You Can Never Say on Television" -- in which he rattles off seven obscenities that are beeped on TV -- led all the way to a Supreme Court ruling.

I'm not here to eulogize the star. Instead, I want to pay tribute to the legendary comedian by going over the seven words that are taboo on Wall Street.

1. Backdating
The stock-option backdating scandal, in which dozens of companies were caught rewriting the dates of option grants to correspond to the lowest actual trading price during any given year, snagged a ton of tech darlings in 2006. Some, like Apple (NASDAQ:AAPL) and Pixar, managed to escape relatively unscathed, but executive shakeouts took place at others, such as CNET Networks (NASDAQ:CNET).

The practice itself wasn't illegal. The issue was that the companies failed to account for the maneuver in public filings. However, in the court of public opinion, backdating felt dishonest, tainting the practice of granting options as an incentive when the prices are handicapped.

2. Enron
It's been seven years since Enron's catastrophic collapse, yet it feels like yesterday that the energy-trading company was caught peppering results with bogus transactions.

The timing of the meltdown of Enron's deceptions, coming shortly after the dot-com bubble burst, was a one-two punch for investors who lost confidence in the art of speculation.

3. Subprime
Two years ago, few knew what a subprime mortgage was. However, when home loan originators were caught granting risky mortgages to even riskier borrowers, it was enough to bring the lending industry to its knees. Even a growth-stock darling like Countrywide (NYSE:CFC) was considered fortunate to get a mercy buyout.

4. Penny Stocks
Neophyte investors gravitate to penny stocks, making the flawed assumption that a low share price equals a cheap price. It doesn't. The problem with penny stocks is that for every low-priced stock that becomes a multibagger, you have countless more that never make it out of the starting gate.

Even chasing larger-cap stocks with low prices -- like Sirius Satellite Radio (NASDAQ:SIRI) -- can be risky. Sirius, for example, commands a larger market cap today than it did several years ago. Why? Well, it may be trading at a lower price, but it also has substantially more shares outstanding today than it did when it went public.

5. Margin
Buying on margin -- where investors borrow from a brokerage at a fair interest rate to buy more shares with less up-front capital -- used to be a win-win. Investors got a little more bang for their buck. Brokerage houses made a little money as a lender.

However, that perception has changed because of market volatility; in this environment, even blue chips can collapse. If stocks fall too sharply, margin calls happen. They even happen to companies, as Thornburg Mortgage (NYSE:TMA) investors found out the hard way, after a series of margin calls found the once high-end home loan specialist trading for less than a buck. Penny stock and margin in the same example? I'm really pushing the envelope now, GC!

6. Stop-Loss
Stop-loss orders, the practice of setting automated instructions with your broker for selling a position if it should hit a certain price point, used to be a great way to lock in profits on appreciating positions or stem the losses on duds.

The practice still works that way, but market volatility isn't always kind to the stop-loss addicts. Stocks can dip during the day -- triggering a sale -- only to bounce back splendidly. You also have the unfortunate market surprises, where stocks gap down, forcing stop-loss orders to be triggered at substantially lower prices than their stop-loss requests.

7. Buy
I hope I'm kidding about this one, but after watching market rallies -- over everything from falling oil prices to a strengthening dollar -- fizzle as the trends revert back to form, I'm feeling pretty brave when I step up as a stock buyer.

There's a lot of elbow room in the bull camp. Let's hope that changes sooner rather than later.

Rest well, George.