As near/far as I can tell and others

I have a couple of questions about phrases that look like they should mean opposite things, but actually mean the same thing. Here are the ones I can think of off the top of my head:

[ul]
As near as I can tell = As far as I can tell
I could care less = I couldn’t care less
Inflammable = Flammable
[/ul]

So here are my questions:
(1) Is there a name for phrases/words such as this? If not, any Latin buffs wanna suggest something?

(2) Anyone think of any others?

(3) Is there a “right” choice and a “less right” choice in any case?

Have fun!
Quix

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Same difference
No difference

Take a shit
Leave a shit

Leave a shit? Never heard that one… is it a regional thing? (I’m American, BTW). Thanks for the added ones!

Quix

Some of them are just cases of the sarcastic turn of the prase becoming popular. “Couldn’t care less” makes sense. “Could care less” means you couldn’t care more – you care the absolute maximum amount. So it’s actually being used sarcastically in the latter, but perhaps not conciously. The former is preferred.

Second what SmackFu said. The other two have different shades of meaning. “As far as I can tell” refers to a weaker understanding than “as near as I can tell”, just as “I didn’t get very far” means that you didn’t get as far as “I didn’t get very close”.

“Inflammable” means it it capable of being inflamed, which is stronger than simply being capable of being flamed. “Inflammable” means that it can be set on fire, while “flammable” means that it can be burnt, which is a subtle difference.

No, “could care less” doesn’t mean the same as “couldn’t care more,” or caring the maximum amount. Look at it this way, if you’re driving in a car, you could say, “I could go slower.” This doesn’t mean you’re driving at the absolute maximum. It just means you’re not at a complete stop. “Could care less,” therefore, means that you care to some degree.