It didn't just disappear, though, the story is more interesting than that. England had an outbreak of religious fanaticism, there was a regicide, dictatorship,

It didn't just disappear, though, the story is more interesting than that. England had an outbreak of religious fanaticism, there was a regicide, dictatorship, a bunch of the losers got kicked out of the country and ended up in the colonies. The Dissenters, also known as the Ranters and Levelers, refused to use the formal pronoun, and insisted of calling everyone 'thou'. The pendulum swung pretty hard and English dropped thou entirely in response.