The 1828 dictionary was published by the Highland Society of Scotland with subscriptions raised from Scots around the world, including plantation owners in then Berbice and Demerara on the north coast of South America and Jamaica in the Caribbean.
The dictionary was the first of its kind to get underway but was beaten into publication by another, which was printed in 1825, it is understood.
One of the largest donors was William Munro, owner of Novar Estate in Demerara and at least 160 slaves. He donated £100 for the society’s dictionary in 1822, the equivalent of just under £13,000 today.
The backstory of the dictionary has emerged in a new BBC ALBA documentary, which explores the links between Africa, Scotland and the Highlands and those whose identity is shared between the three.
Musician Cass Ezeji, who presents Trusadh: Afro-Gàidheil - Afro-Gaels, said: “I was so shocked to hear that the first Gaelic dictionary was founded by slave traders. It will take me a while to recover from that. It has changed my opinion a little about the Gaels. It is difficult for me to say. But even for me personally, I also feel unsure about where I fit in with that history.
"It is interesting for me how one community who was oppressed then went on to do the same to another oppressed community.
“It is vital that we speak about this in our community.”
Ms Ezeji made the discovery after interviewing Dr David Alston, author of newly-published Slaves and Highlanders, Silenced Histories of Scotland and the Caribbean.
Other donors to the dictionary included James Fraser of Belladrum, whose father – also James – was key to the involvement of Highland Scots in the plantations of Berbice, according to Dr Alston.
James Jnr, along with other Highlanders, bought up several parcels of land in Berbice, which were then operated as plantations.
James and his two brothers owned several of them, with the Highlander finally returning to Scotland in 1821. By then, his only estate in Berbice was plantation Golden Fleece, where 374 slaves were kept.
The documentary also explores subscriptions paid to a fundraiser for ‘Highland destitution’ in 1837.
Bad weather and poor harvests in 1835 and 1836 led to food shortages with committees formed in Edinburgh, Glasgow and London to raise public subscription from the rest of Great Britain, Ireland and the colonies.
Remarkably, donors included former slaves who served as indentured servants following abolition.
Funds were used to buy seed, food and clothing with analysis by Dr Alston showing donations from “apprentice labourers” from the “plantation industry” in Demerara.
Dr Alston said: “This is at the end of slavery but former slaves were bound to unpaid work to their masters for five years.
"They are inbetween slavery and freedom
"So you have former black slaves sending money for destitute Highlanders.”
Ms Ezeji, from Glasgow, attended the city’s first Gaelic primary school in Ashley Street.
She said she always felt “conflicted” about her Gaelic-speaking identity and her African heritage.
Ms Ezeji said: “I didn’t appreciated I was part of the Gaelic world. I didn’t see myself as part of the culture. There was something of a disconnect.”