The strathspey The Shakin's o' the Pocky was composed by the renowned Scottish fiddler James Scott Skinner, in collaboration with his former teacher, Peter Milne.  "Pocky" has nothing at all to do with the Pox; in this context, it just means "a bag" (same word as "pocket", basically).  For more information, see the entry at The Fiddler's Companion:  Results of Search for Pocky

The song Shaking of the Sheets seems to be completely unrelated.  Of the two sets in the DT, The one recorded by Steeleye Span appears to be a modernised re-write by them of the other.

Malcolm