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Why are some words added ' at the ending of?( flyin’ swarmin’ an’)
For example: He fell asleep as we was flyin’ over Bristol.”
They started swarmin’ around.
... an’ poor little Harry off ter live with them.
flyin’ swarmin’ an’

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 "But I c-c-can't stand it -- Lily an' James dead -- an' poor little Harry off ter live with Muggles -" 

This is an example of "eye dialect" writing. The author is writing the words as the speaker would say them, phonetically. The missing sounds are replaced by the apostrophe.

Notice the stutter at the initial "c" in "Can't"

Here is a line from George Bernard Shaw's play "Pygmalion"


"Cheer ap, Keptin; n' haw ya flahr orf a pore gel."

Comments  
linguist777Why are some words added ' at the ending of?

Why do some words have an apostrophe added on at the end?

One of the functions of the apostrophe is to indicate omitted letters. It is used that way in contractions like "don't" (do not) and "you're" (you are). It is used that way in your examples of quoted speech as a way of writing the way a person pronounces a word, sometimes called "eye dialect". People everywhere often drop the "g" sound in "-ing" verbs, and certain dialects tend to say "and" without the final "d" sound.

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