English is not a fixed language so with time, words tend to come in more often and become acceptable.
These words are commonly called pseudoatonmys
Looking at the above words, first thing that comes to the mind is, one catches fire and the other doesn't. Actually they mean the same thing.
Bar being the act of prohibition, funny enough debar also means the same thing.
Regardless, prevailing against odds and circumstances. Irregardless is likely originated from a combination of 'irrespective' and 'regardless' and thus became accepted.
Habitable simple implies Suitable to live in. You would think inhabitable was any different, but it means the same thing.
Everyone has probably heard of genius. Clever, inventive person, and exceptional intellect. Ingenious also implies the same thing.
To terminate, the act of bringing to an end of something. Your guess would be with the prefix of 'ex' there would be difference but it does almost mean the same thing.
Your first opinion of restive would be in a state of rest, but restive actually means being unable to stay silent or still, thereby restlessness.
Valuable means of great worth. Invaluable also means the same thing, being useful and indispensable.
Have a fun-filler Sunday to all Waploadites ;D ;D