I read the following on page 175 of "Conamara Chronicles: Tales from Iorras Aithneach", the 1941 Irish folklore book compiled by Seán Mac Giollarnáth that was translated by Tim Robinson and Liam Mac Con Iomaire and reissued in 2022:

“She bought enough adhairí to go on the edge of the sail – the adhaire is a heavy hempen rope.”

Is anyone familiar with adhaire as meaning hemp rope? I’ve looked in the usual online places (e.g., Teanglann), but only came up with súgán for hemp rope and cnáib for hemp.

Is (or was) adhaire a local usage in Connemara or maybe only in that part of Connemara?

I think a súgán is mostly made of grass straw, but you could make it out of any fibre I suppose.

Living in Conamara I’ve never heard of anybody growing hemp. Possibly it was more common in the past, but today it’s illegal to grow without a license.
Cnáib was the only word I could find online too (pronounced with a R).

Googling sailing ropes I see they’re often made of manila hemp, which isn’t real hemp at all but a banana plant.
I see it’s available to buy in Ireland from a number of boating suppliers. That could be what the woman bought.
A handmade súgán wouldn’t be strong enough to be used in boating. Rope would be bought, not made locally.

Thank you Bríd for your comments. I did some quick research and came up with the following historical and linguistic information. There are loads of articles, both scholarly and popular, on the subject of hemp in Ireland. Nothing I saw addressed my initial question about the use of "adhaire" for hemp rope.

https://journals.sagepub.com/doi/10.1089/can.2022.0263

Words for “hemp” in Celtic languages are loanwords, not cognates. The Irish word cnáib is first attested in texts written 1060 and 1127–1134 CE.… Pollen consistent with cultivated Cannabis appears in the Middle Ages, ca. 700 CE, at sites in the vicinity of monasteries. Archaeological finds (hemp seeds and fiber) date to later Norse-Viking and Anglo-Norman sites.
Cnáib is absent in Old Irish glossaries, epics, and mythologies (600–900 CE) …. data suggest that the onset of hemp cultivation correlated—chronologically and spatially—with the founding of Romano-British monasteries. Irish cnáib was likely borrowed from Clerical Latin canapis or canabus.

Google AI Overview:

Hemp has a long history in Ireland stretching back over 1,050 years, closely tied to monastic introduction, maritime trade, and British naval ambitions.
Early Introduction and the Middle Ages
• Monastic cultivation: Fossil pollen studies show that Cannabis cultivation appeared in Ireland around 700 CE near early Christian monasteries.
• Linguistic roots: The Irish word for hemp, cnáib, is a late loan word derived from clerical Latin.
• First written records: Gerald of Wales documented commercial hemp production in Limerick in his 1188 text, Topographia Hibernica. An 850-year-old piece of hemp cord preserved in the Dublin City Archives provides physical evidence from this era.
British Rule and Naval Demands
• Colonial promotion: Queen Elizabeth I and later monarchs encouraged Irish farmers to grow hemp to supply the growing English textile and shipping sectors.
• The Napoleonic Wars: By 1808, Britain faced severe supply blockades and relied heavily on the Royal Navy. The British government proposed draining Irish peat bogs to clear over a million acres of land dedicated exclusively to hemp cultivation for ship sails and rigging.