though Etymology: For Middle English þof —See Þoȝ
Of.—“A child of four years old.” Say “a child four years old,” or “a child of four years.”
prep. and adv. of, out of, from, by, offVariants: o,off, aEtymology: Anglo-Saxon of : Gothic af : Old High German aba : Greek ἀπό; 0.

of : That the force of this word is not fully understood is proved by the fact that many ministers choose to omit it from the title of Scriptural books. Dean Alford in referring to the habit of announcing “The Book Genesis” instead of “The Book of Genesis,” says, “This simply betrays the ignorance of the meaning of the preposition of. It is used to denote authorship, as the Book of Daniel; to denote subject matter, as the first Book of Kings; and as a note of apposition signifying which is called, as the Book of Genesis.... The pedant, who ignores of in the reading-desk must however, to be consistent, omit it elsewhere: I left the city London, and passed through County Kent, leaving realm England at town Dover.” Of is also frequently misused for from. Nothing but custom can justify the common form of receipt, “Received of...”.