Dr Garry Tregidga, co-director of the University of Exeter’s Institute for Cornish Studies, said while the error was “embarrassing” for Tesco, it was also “great if there was the intention to have signs in Cornish”.
He added: “What is also positive is that this mistake was spotted. This is a sign of the increasing number of people who are using and recognising Cornish.
“If anyone from Tesco needs assistance putting together the new signs there are plenty of people who would be glad to help.”
Last month the Cornish language was given extra protection through the European Charter for Regional or Minority Languages.
The move gives it the same level of protection as all the other Celtic languages recognised across the British Isles, including Welsh.
Like Welsh, Kernewek is a Brythonic Celtic language. The two languages, along with Breton, are closely related.
There are about 400 to 500 advanced speakers of Cornish, with between 2,500 and 5,000 people having some basic knowledge.
The Cornish people are a recognised national minority under the European Framework Convention for the Protection of National Minorities, meaning they share the same status as the Welsh, Irish and Scots within the UK.
In the 2021 census, more than 100,000 people expressed their main national identity, ethnicity or main language as Cornish.