I've had a fair amount of experience in branding, both writing about it and actually doing it (in a Fortune 500 company). Over the years, I've come to the conclusion that there is only one truly important rule when it comes to naming a startup.
I call it the OMC rule, which stands for "Obviously Meaningful to Customers." To help you understand the value of OMC, I'll break it into chunks:

"Obviously"

A company name should not require a customer, investor, or employee to expend mental effort deciphering its meaning. If a company name requires an explanation, it's not following this part of the rule. Examples:
  • Poiuyt Inc. ("It's the top of the left hand side of the QWERTY keyboard and it means that we think differently.")
  • Calibrex5D ("We help companies work through the '5 Ds' of the engineering process; here's a 12 page presentation that explains this.")

"Meaningful"

There's a huge difference between being meaningful and just having a meaning. Anything can have a meaning, in the sense of a definition. For example, the word "ommatophor" has a meaning. However, it's only meaningful to a biologist. Or a snail, if it could talk.
For a company name to be meaningful, in addition to having a meaning, it must create a positive emotion. Here are some examples of company names that have meaning but are not meaningful (i.e., evoke no emotion):
  • Market Consulting Inc. (OK, yeah, we know from the name kinda what you're all about but ... meh.)
  • Analog Widget Corp. (Yes, yes, you make widgets. Thanks for telling me. But why should I care?)

"to Customers"

It's not enough to just be meaningful, though. To be effective the name must be meaningful to potential customers and, by extension, to potential investors and potential employees, too.
Here are some examples of names that would be meaningful to the people inside a company, but carry no emotional weight with outsiders:
  • Optimal Associates. (Yes, you're an association that wants to optimal, but what does that mean to me?)
  • The Smithson Group. (Yup, somebody named Smithson founded the company. Why should I care?)
Now that I've provided some bad examples, here are some examples of great startup names that ended up as huge companies. To make this easy, I'll put those names into three generic types:

Retro-Ironic Descriptors

These are longish names that describe the product or service but with an old-timey feel and a slightly ironic edge. Examples:
  • The Cheesecake Factory
  • Urban Outfitters
  • Great American Cookies
Traditionally, it's been consumer companies that have used retro-ironic descriptors. Most B2B firms would probably consider them a bit too frivolous.

Emotion-Laden Actual Words

These are real words or combinations of real words that communicate meaning and also carry emotional overtones (i.e., are meaningful). Examples:
  • Uber
  • Life Is Good
  • Oracle
Unfortunately, it's become almost impossible nowadays to find usable real words to name your company. By now they've mostly been snatched up, either as trademarks, URLs, or both. Never hurts to look, though.

Suggestive Neologisms

These are made-up words that attempt to capture both the meaning and meaningfulness of real words. Examples:
  • Lyft
  • Activa
  • Integra
Unlike actual words, neologisms can usually be trademarked and have an available URL. However, neologisms have become so common that they can seem a bit bland.
BTW, once a firm has established itself, these rules don't apply. Apple, for example, was a bit of a head-scratcher when it first appeared. However, the Apple name acquired meaning (and meaningful emotion) after people used the products.
In other words, while Apple is today a fabulously valuable brand, if you're starting a new company, naming your firm "Avocado" or "Cashew" isn't going to be much help. If you follow the OMC rule, though, your company name can be a real asset.
If your startup name isn't OMC, don't despair. Eventually, your success (or lack of it) will create both meaning and meaningfulness to your customers, investors and employees. Whether you become a "Cisco" or an "Enron" is entirely up to you.