O-f

1.
Old French.
/ɒv; unstressed əv/
preposition
1.
used with a verbal noun or gerund to link it with a following noun that is either the subject or the object of the verb embedded in the gerund: the breathing of a fine swimmer (subject), the breathing of clean air (object)
2.
used to indicate possession, origin, or association: the house of my sister, to die of hunger
3.
used after words or phrases expressing quantities: a pint of milk
4.
constituted by, containing, or characterized by: a family of idiots, a rod of iron, a man of some depth
5.
used to indicate separation, as in time or space: within a mile of the town, within ten minutes of the beginning of the concert
6.
used to mark apposition: the city of Naples, a speech on the subject of archaeology
7.
about; concerning: speak to me of love
8.
used in passive constructions to indicate the agent: he was beloved of all
9.
(informal) used to indicate a day or part of a period of time when some activity habitually occurs: I go to the pub of an evening
10.
(US) before the hour of: a quarter of nine
abbreviation
1.
Old French (language)
prep.

Old English of, unstressed form of æf (prep., adv.) “away, away from,” from Proto-Germanic *af (cf. Old Norse af, Old Frisian af, of “of,” Dutch af “off, down,” German ab “off, from, down”), from PIE *apo- “off, away” (see apo-). Primary sense in Old English still was “away,” but shifted in Middle English with use of the word to translate Latin de, ex, and especially Old French de, which had come to be the substitute for the genitive case. “Of shares with another word of the same length, as, the evil glory of being accessory to more crimes against grammar than any other.” [Fowler]

Also from 1837 a non-standard or dialectal representation of have as pronounced in unstressed positions (could of, must of, etc.)

verb

Have •In verb constructions, used for humorous or dialect effect: I must of gone crazy or something (1844+)
1.
Oriental female
2.
outfield
3.
outfielder