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a remnant from the Anglo-Saxon where there was a slight difference between 'sendan' and 'onsenden'.

Cool! I wasn't aware of that structure.

I think we tend to add words to give a slight difference in meaning as well,

I can see it in some instances -- the difference between 'cried' and 'cried out' that sidlj mentioned. But if there's a difference between 'shouted' and 'shouted out', it's too slight for me to notice. Perhaps there's a regional variation and/or meaning that others might not recognize.
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