The first photographic images widely used were known as daguerreotypes after the technique used.  (There were other techniques and names in the 1840s and 50s, eg calotype, ambrotype, but daguerreotype was the first.)

Later on we started calling them the more generic term photograph, but exactly when did we start doing that?

For example Beard, the first commercial daguerreotypist in Britain, was still calling them daguerreotypes as late as 1855, but the diarist Francis Kilvert, writing in 1870, refers only to photographs.

Well to find out I did some very simple investigations – first of all I used the Google Ngram viewer to look at the yearly occurrence of the term daguerreotype in the English corpus:

which gives us a peak usage of the term around 1853 or 1854.

Again using the Google Ngram viewer I compared the occurrence of the term daguerreotype versus photograph over the period 1840 to 1860:

and we can see that the crossover occurred around 1855.

To sanity check this I then checked the relative occurrence of the two terms in both Welsh Newspapers online and the NLA’ s Trove. As the Trove dataset is richer I graphed the two of them separately to stop the Welsh data being drowned out the Trove data.

So, in the Welsh data we see that the data more or less matches the Google Ngram data with the crossover occurring about 1855. Interestingly, the Trove data shows something else, with both terms being used equally in the first few years of the 1850’s, with use of the term photograph taking off in 1856.

1855 of course was the date of Roger Fenton’s seminal Crimean War images, and in reports of the exhibition of his photographs, reporters use the term photograph, rather than referring to the particular technique used, suggesting perhaps that this helped drive the initial adoption of the term in preference to daguerreotype …