There is little or no difference between the -one and -body variants.
However, there is a major difference between somebody and anybody--anybody is one of the "negative valency" words in English, which is required when the main verb of the sentence is negated.
I haven't seen anybody. [Correct]
! I haven't seen somebody. [Incorrect]
Conversely, in sentences in which the main verb is affirmative (not negated), the preferred pronoun should be somebody and not anybody.
I saw somebody in the hall. [Correct]
! I saw anybody in the hall. [Incorrect]
In subject position, you should prefer somebody when a particular person is implied, although you don't know who it is. Anybody can be used when you have no particular person in mind.
Somebody called me on the phone. [Correct]
! Anybody called me on the phone. [Incorrect]
? Somebody can come to the party. [Not exactly incorrect, but very strange--it implies that there is a single, unnamed person that can come to the party.]
Anybody can come to the party. [Correct]
To did not come from unto (if anything, vice versa), so the situation is not the same as with flammable and inflammable. Though to is an older form, unto was never as prevalent, and is now either archaic, or used in limited contexts, such as shown here (Idiom: unto itself).
Best Answer
Both refer to short-lived things or activities or events. Transient implies some kind of transition between states in which the transient state does not last very long.