Thanks for the mumpsimus explanation Mr Red. Bit like the dancers who, having learnt the Cecil Sharp invention of 'siding' when he didn't know the meaning of a common term in Playford's Dancing Master of 1651, then wouldn't let him change the dances when research worked out a more plausible figure. So callers still have to specify 'Cecil Sharp siding' or 'Into line siding' and there are still some who call Cecil Sharp's version "the proper siding".