AnnaStrophic wrote:
>In the same vein, there are words that seem to be antonyms but are in fact synonyms, such as "flammable" and "inflammable."

This happens because the prefix in- is usually thought of as "not" but also can mean in/into/upon. Here again, there were two root words from Latin: flammare and inflammare.

Other pseudo-antonyms are ravel/unravel, bone/debone and loose/unloose. Ravel is quite interesting in as it can mean disentangle or unravel, or it can mean confuse or entangle -- it's a contronym as well!