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This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

The settlement of Plympton, further up the River Plym than the current Plymouth, was also an early trading port, but the river silted up in the early 11th century and forced the mariners and merchants to settle at the current day Barbican near the river mouth. At the time this village was called Sutton, meaning south town in Old English. The name Plym Mouth, meaning "mouth of the River Plym" was first mentioned in a Pipe Roll of 1211. The name Plymouth first officially replaced Sutton in a charter of King Henry VI in 1440. See Plympton for the derivation of the name Plym.
Output:
In what century were sailors obligated to relocate from Plympton due to silting?