IOLAGAN, VI 166: The reason why daughters-in-law and mothers-in-law can never agree is that the devil is said to have shaken iolagan between them. Tha ’n droch-spiorad crathadh iolagan eadar bhana-chleimhnean. What these iolagan are I don’t know and can’t find out. Iolagan or Iollag, 43 = ? (If not links of devil’s chain). ’S e dh’fhàg na bana-chleimhnean gun bhith rèidh, gun do chrathadh na h-iollagan eatorra, [what prevented the female in-laws being at peace was that the iollagan had been shaken between them].
It was noted down in Garrynamonie in 1988-9 that iolag/an was/were links in a chain.
Dwelly has no clues, except for iullag: “Sprightly, affected little female; skip, trip.” I imagine that shaking affected little females between women might certainly annoy them, but I think the chain suggestion more likely.