I came across the following etymology for "liberty" here.
Liberty - The Latin words "Liber," "Libera," and "Liberum" -- with a Long I -- came from the root meaning, "to pour." From this, we get the word "Liberty" (hence pronounced with a short I), from the freedom we feel when we get drunk.
As far as I can tell from my Internet explorations, this isn't true, and they're mixing up "liber" with "libare." However, I'm not very knowledgeable about Latin, so I thought I'd get a second opinion.
If it's not true, I'd be interested in other examples of words that have gone through really startling semantic change. Specifically words that involve ideology or value judgments (sophisticated and heresy are examples I've got so far.)