A couple recent articles about the history of the ellipsis, drawing on the new book Ellipsis in English Literature: Signs of Omission by Anne Toner, which I have not read yet but looks interesting.
From the Guardian:
“There is no play printed before Kyffin’s Andria and listed in WW Greg’s Bibliography of English Printed Drama that marks unfinished sentences in this way. This is not to say that these were the first ellipses in English print. There are appearances of the mark earlier in the 1580s. Henry Woudhuysen has identified dashes in letters printed in 1580 and 1585, where in both cases the mark occurs as part of an informal, conversational style.”
But drama was “especially important” in the evolution of the ellipsis, according to Toner, being the literary form “that is connected in the most concentrated way with speech as it is spoken”. And after its appearance in the 1588 Andria, the punctuation mark quickly caught on. […]
Embraced by writers from Percy Shelley to Virginia Woolf, it was in the novel that the ellipsis “proliferated most spectacularly”, according to Toner. She points to Ford Madox Ford and Joseph Conrad’s use of ellipses more than 400 times in their 1901 novel The Inheritors. Ford said that the writers were aiming to capture “the sort of indefiniteness that is characteristic of all human conversations, and particularly of all English conversations, that are almost always conducted entirely by means of allusions and unfinished sentences”.
In medieval manuscripts, we find a mark—sometimes called subpuncting or underdotting—that is used to indicate the omission of a word or phrase, usually when that word or phrase has been copied erroneously. This omission mark involves placing a series of dots under the word that is to be omitted. The image below shows an erroneous word, blotted out and subpuncted: