Bring One's Arse To An Anchor Meaning

(idiomatic, rare) To sit down.

Example: 1983, Hugh Oram, The Newspaper Book: A History of Newspapers in Ireland, 1649-1983, page 182,
  The young Fleming went in search of Smyllie in the Palace Bar, where he and his group were discussing the arguments for and against the Resurrection. "Bring your arse to an anchor, boy," Smyllie instructed Fleming, before ordering him to come for a formal […] .
1988, J. Nazareth, The Psychology Of Military Humour, page 181,
  â€˜Well, in that case,’ said Kelly, ‘bring your arse to an anchor,’ inviting him to sit down.