A correspondent writes to ask about the possessive apostrophe. Is it actually an apostrophe of omission?
The apostrophe is a relatively late arrival in English. Its origins lie in Europe, where early 16th century printers introduced it (based on Greek practice) to show the omission of a letter (usually, showing the elision of a vowel in speech). The earliest appearance of it in England is in a book printed by John Day in 1559, William Cunningham's The cosmographical glasse. It was definitely seen as a sign of omission. Ben Jonson describes it as 'the rejecting of a vowel from the beginning or end of a word', such as we would see in heav'n or desir'st. And this is how it was with the possessives, where it was originally used to show the omission of an e, as in dogges - and also to mark a plural, especially of foreign words (where folioes would be written as folio's).
In the seventeenth century, practice slowly standardized. The use to mark the e in a plural died away (though not entirely - it can still be found in the quotations in Johnson's Dictionary of 1755), and the use to mark a possessive extended to all cases of possession, whether there was an original e there or not. So we find, in the 18th century, such forms as woman's as well as for conscience' sake. 19th-century printers then developed the rules which made the distinction between singular and plural possession (cat's vs cats') - though not without some opposition from grammarians. The OED has a nice example from Mason's English Grammar of 1876 which shows how the idea of elision was still present in people's minds : 'It is an unmeaning process to put the apostrophe after the [possessive] plural s (as birds'), because no vowel has been dropped there'.