And I am certain that the actual form of shoogly was influenced by cugallach. Its first citation in DSL is 1822, even though the verb, and the present participle (shooglin etc., used as an adjective) are much older. My guess is that it was Gaels coming to the Lowlands that developed shooglin (meaning actually shaking) into shoogly meaning 'cugallach', 'loose', 'precarious'.
I cannot find an etymology for cugallach.
Just another thought
My Grandmother was Daisy Johnson was born in India 1905 her father Robert was born, lived and died in India and Grandfather Thomas was likely to have been as well ca 1820’s as he was a bandmaster ( in the East India Company Madras Native Infantry) and bandsmen tended to be sons or grandsons of British soldiers
There is a word that she taught me which she pronounced as “Coojlee” It is the shakey feeling I had with respect to balloons that had gone all wrinkly and I didn’t like touching it. I would say it made me feel all coojlee
Over the years I realised that this word was not used in other parts of the family or by their friends in the Anglo-Indian Community. Nothing similar in “Hobson Jobson” Glossary for British India
So I was surprised years later , in fact when I first began Gaelic in 1991, to find their was a similar word shoogly, but was Scottish.
Looking at the time line the Clearances had begun in the mid 18th Century and the East India Company were recruiting n the Highlands according to one sources I looked at.
I did wonder in the past , and coming across this discussion brought it to mind, might this word have come down to my Grandmother from her Johnson ancestors, having been transported across the world from Scotland to India
I just realised that you can look at the Gaelic Dictionary by Dewlly online on the following site ( I have long since passed on mine as I was no longer “ having need of it”!
Yes. That is a great portal with two dictionaries in it. I have a great collection of perhaps 20 paper dictionaries in a number of languages and I have not opened any of them recently, and I probably never will again. Online versions are just so much better, specially in a minority language where most dictionaries, like Dwelly, only translate into English. With the online version you can put in any English word and find all the Gaelic words that include it in the translation. With the Celtic languages it is also particularly helpful to be look up a mutated form and it finds the word. (This is even more helpful in Welsh etc. because of their spelling system.)