Dwelly has gog for a nod or a tossing of the head (as well as a hen clucking or pigeon cooing), and gogadh for tossing the head too (cha’n e gogadh nan ceann a ni an t-iomram, it is not the nodding of the heads that rows the boat.) Gogaideachd is coquettishness, “womanish vanity”.
Three references in DASG all talk of gogadaich like a hen or a cock.
Màiri Thormoid from Eriskay knows it for somebody with their head going up and down.
One person who wished to remain nameless had me laughing with this example: “I think you’d say that about that one with the dress in the parliament – Nicola – she’s always a’ gogadaich! Have you ever noticed?”
John Archie MacMillan from South Uist says gogadaich is “talking too much, especially at the back of church when you’re supposed to be quiet, or in class at school.”
Another woman from Eriskay tells me that gogadaich is almost onomatopoeiac – “talking nonsense, also chuckling. You could say of someone poorly or sad, or drunk, ‘He nearly had goc.’ ”