one "off" - Sorry folks, it's actually incorrect usage.
For example, would you say or write, "one off a kind", or, "one of a kind", because that's exactly what "one of" means. It means, "one of a kind", unique, different from all others. The word, "off" is incorrectly used in this case.
of
(ŭv, ŏv; əv when unstressed)prep.1. Derived or coming from; originating at or from: customs of the South.
2. Caused by; resulting from: a death of tuberculosis.
3. Away from; at a distance from: a mile east of here.
4. So as to be separated or relieved from: robbed of one's dignity; cured of distemper.
5. From the total or group comprising: give of one's time; two of my friends; most of the cases.
6. Composed or made from: a dress of silk.
7. Associated with or adhering to: people of your religion.
8. Belonging or connected to: the rungs of a ladder.
9.a. Possessing; having: a person of honor.
b. On one's part: very nice of you.
10. Containing or carrying: a basket of groceries.
11. Specified as; named or called: a depth of ten feet; the Garden of Eden.
12. Centering on; directed toward: a love of horses.
13. Produced by; issuing from: products of the vine.
14. Characterized or identified by: a year of famine.
15.a. With reference to; about: think highly of her proposals; will speak of it later.
b. In respect to: slow of speech.
16. Set aside for; taken up by: a day of rest.
17. Before; until: five minutes of two.
18. During or on a specified time: of recent years.
19. By: beloved of the family.
20. Used to indicate an appositive: that idiot of a driver.
21. Archaic On: "A plague of all cowards, I say" (Shakespeare).
[HR][/HR]
[Middle English, from Old English; see apo- in Indo-European roots.]
off
(ôf, ŏf)adv.1. From a place or position: He walked off in a huff.
2.a. At a certain distance in space or time: a mile off; a week off.
b. From a given course or route; aside: The car swerved off into a ditch.
c. Into a state of unconsciousness: I must have dozed off.
3.a. So as to be no longer on, attached, or connected: He shaved off his mustache.
b. So as to be divided: We marked off the playing field by yards.
4. So as to be no longer continuing, operating, or functioning: She switched off the radio.
5. So as to be completely removed, finished, or eliminated: Will the cats kill off the mice?
6. So as to be in a state of sudden violent or loud activity: The firecracker went off. The alarm went off.
7. So as to be smaller, fewer, or less: Sales dropped off.
8. So as to be away from or not engaged in work or duty: They took a day off.
9. Offstage.
adj.1.a. Distant or removed; farther: the off side of the barn.
b. Remote; slim: stopped by on the off chance that they're home.
2. Not on, attached, or connected: with my shoes off.
3. Not operating or operational: The oven is off.
4. No longer taking place; canceled: The wedding is off.
5. Slack: Production was off this year.
6.a. Not up to standard; below a normal or satisfactory level: Your pitching is off today.
b. Not accurate; incorrect: Your statistical results are off.
c. Somewhat crazy; eccentric: I think that person is a little off.
7. Started on the way; going: I'm off to see of in Indo-European roots.]
Usage Note: The compound preposition off of is generally regarded as informal and is best avoided in formal speech and writing: Hestepped off (not off of) the platform. Off is informal as well when used to indicate a source. Formal style requires I borrowed it from (notoff) my brother.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Of - definition of of by The Free Dictionary
Off - definition of off by The Free Dictionary