In 1860, Mark Antony Lower, in his 'Patronymica Britannica, a dictionary of the family names of the United Kingdom', said simply that Nimmo was “a Scottish surname derived from lands in co. Stirling.” Two years later, Clifford Stanley Sims, researching from the United States, wrote 'The Origin and Signification of Scottish Surnames: With a Vocabulary of Christian Names' and agreed with Lower, claiming that Nimmo was “a local surname originating from the lands of Nimmo in Stirlingshire”.
In 1946, George Fraser Black wrote 'The Surnames of Scotland: Their Origin, Meaning, and History'. In the introduction to that tome, he suggested that Nimmo probably resulted from a “laziness of utterance” when 'ch' like 'ck' was dropped off
In 2007, Elizabeth Caldwell Hirschman and Donald Neal Yates published an interesting book called 'When Scotland Was Jewish: DNA Evidence, Archeology, Analysis of Migrations, and Public and Family Records Show Twelfth Century Semitic Roots'. In that book, the authors suggest that Nimmo means “from Nîmes”, a town dating back to the Roman Empire in southern France. Interestingly, family legend has suggested that our Nimmo's were Jewish.
The oft-repeated origins of Nimmo found online suggest that it has a Latin origin, meaning “no name” and that it was often given as a last name to children of unknown parentage. I am yet to find a scholarly basis for this, and would welcome someone pointing me in the direction of a reliable source (if one exists).
So, which Nimmo’s do I know about? I think that will have to wait for another post!