One of the parameters to Unix command 'dd', which presumably means 'output file'. According to man page:

dd - convert and copy a file
of=FILE - write to FILE instead of stdout

'Of' is an odd word. Not semantically, of course. It is a perfectly cromulent word as far as meaning goes. However orthographically and etymologically it is a train wreck. It is spelled, as you can see, with an 'o' and an 'f', but it is pronounced as 'uv'. It is the only word in the English language in which F is pronounced as /v/1. It is also the twin to the more regularly pronounced word 'off' -- in fact, they are identical twins, and an excellent example of how environmental factors can warp development.

'Of' comes from the Old English æf, meaning 'away', or 'away from'. Over time æf came to exist in two forms; the stressed or emphatic /æf/ was used when it functioned as an adverb ("he went off"), and the unstressed /æv/ when used in the genitive case ("Author of Camelot"). But while these were pronounced differently, for a long time this was not considered an important difference, and did not appear in writing2. In Old English /v/ was an allophone of /f/; while the sounds were usually pronounced differently depending on where they appeared in words or sentences, they were not considered different letters, and were both represented by the letter F.

This started to change after the Norman Conquest introduced a large chunk of French vocabulary into England. The Old French language introduced the importance of distinguishing /v/ from /f/, as these were distinct phonemes in French. Over the coming years (c.1154-1470) most words pronounced with a /v/ sound gained a V; ofer became over, etc. Unfortunately, this distinction passed over 'of', largely because the of/off split was not widely recognized in a formalized manner until the 1600s. Until then the spelling was fluid, so the exact differences between æf, of, and off were not systematic. This split took place long after the other /v/ sounds had gained a firm toehold in print.

Even though of/off split lagged behind the F/V split, they were both caused by the influx of Old French. Old French distinguishes between de (of) and ab- (off). Gradually Middle English/Early Modern English translators started to realize that they could no longer always treat these two meanings of æf/of/off as equal. Our odd spelling of 'of' comes from the happenstance that English was quicker to pick up a new sound than a new meaning.


1. The slash marks (/v/) are used to indicate that this is a phonetic representation of how the letter or word sounds, as opposed to how it is spelled. I will be using this convention throughout the writeup, as is standard practice when working with phonological transcription. All sounds are written using the International Phonetic Alphabet.

2. We do the same thing in Modern English -- and we do it a lot. We "have a cat", but we "haff to wash the cat". We "opened the door", but we "shopt in the store". This sort of thing drives second graders who are learning to spell absolutely crazy, and then we forget about it.

Of (?), prep. [AS. of of, from, off; akin to D. & OS. af, G. ab off, OHG. aba from, away, Icel., Dan., Sw., & Goth. af, L. ab, Gr. , Skr. apa. Cf.Off, A- (2), Ab-, After, Epi-.]

In a general sense, from, or out from; proceeding from; belonging to; relating to; concerning; -- used in a variety of applications; as:


Denoting that from which anything proceeds; indicating origin, source, descent, and the like; as, he is of a race of kings; he is of noble blood.

That holy thing which shall be born of thee shall be called the Son of God. Luke i. 35.

I have received of the Lord that which also I delivered unto you. 1 Cor. xi. 23.


Denoting possession or ownership, or the relation of subject to attribute; as, the apartment of the consul: the power of the king; a man of courage; the gate of heaven.

"Poor of spirit."



Denoting the material of which anything is composed, or that which it contains; as, a throne of gold; a sword of steel; a wreath of mist; a cup of water.


Denoting part of an aggregate or whole; belonging to a number or quantity mentioned; out of; from amongst; as, of this little he had some to spare; some of the mines were unproductive; most of the company.

<-- partative genitive -->

It is of the Lord's mercies that we are not consumed. Lam. iii. 22.

It is a duty to communicate of those blessings we have received. Franklin.


Denoting that by which a person or thing is actuated or impelled; also, the source of a purpose or action; as, they went of their own will; no body can move of itself; he did it of necessity.

<-- = out of, from, due to -->

For it was of the Lord to harden their hearts. Josh. xi. 20.


Denoting reference to a thing; about; concerning; relating to; as, to boast of one's achievements.

Knew you of this fair work? Shak.


Denoting nearness or distance, either in space or time; from; as, within a league of the town; within an hour of the appointed time.


Denoting identity or equivalence; -- used with a name or appellation, and equivalent to the relation of apposition; as, the continent of America; the city of Rome; the Island of Cuba.

<-- always preceded by a type name? -->


Denoting the agent, or person by whom, or thing by which, anything is, or is done; by.

And told to her of [by] some. Chaucer.

He taught in their synagogues, being glorified of all. Luke iv. 15.

[Jesus] being forty days tempted of the devil. Luke iv. 1, 2.

The use of the word in this sense, as applied to persons, is nearly obsolete.


Denoting relation to place or time; belonging to, or connected with; as, men of Athens; the people of the Middle Ages; in the days of Herod.


Denoting passage from one state to another; from.

[Obs.] "O miserable of happy."



During; in the course of.

Not be seen to wink of all the day. Shak.

My custom always of the afternoon. Shak.

Of may be used in a subjective or an objective sense. "The love of God" may mean, our love for God, or God's love for us.

From is the primary sense of this preposition; a sense retained in off, the same word differently written for distinction. But this radical sense disappears in most of its application; as, a man of genius; a man of rare endowments; a fossil of a red color, or of an hexagonal figure; he lost all hope of relief; an affair of the cabinet; he is a man of decayed fortune; what is the price of corn? In these and similar phrases, of denotes property or possession, or a relation of some sort involving connection. These applications, however all proceeded from the same primary sense. That which proceeds from, or is produced by, a person or thing, either has had, or still has, a close connection with the same; and hence the word was applied to cases of mere connection, not involving at all the idea of separation.

Of consequence, of importance, value, or influence. -- Of late, recently; in time not long past. -- Of old, formerly; in time long past. -- Of one's self, by one's self; without help or prompting; spontaneously.

Why, knows not Montague, that of itself England is safe, if true within itself? Shak.


© Webster 1913.

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