Etymology of "cluster" in the context of cluster analysis I'm trying to track down the origins of the word "cluster" and its usage in the context of cluster analysis.
Please, does anyone know when and by whom it was first used? Perhaps there was a paper or a book which coined these terms?
Alternatively, maybe there is some literature describing the beginnings of the fields which work with the term "cluster" such as machine learning or statistics of some kind?
 A: "Cluster of rocks", "cluster of islands", "cluster of factories" etc. can easily be traced back to the 19th century (and probably much longer). Of course statistics early on started to look for a way to formalize this. So good luck, you will likely need to walk to a lot of libraries (the physical one, not the software library)!
Don't look at "machine learning". ML did not invent cluster analysis; and  most cluster analysis research happens outside the ML community.
The term "cluster analysis" dates back to the 1930s statistics; but you can imagine that "cluster" in the notion above was used much earlier - but cluster analysis attempts at discovery exactly this notion of "clusters".
Many of the early usage was on clustering observations in nature, such as species; either by location or by similarity. No computers involved: it probably wasn't until 1957 when the first algorithms for "cluster analysis" arrived (before that, cluster analysis was "pen & paper")

P. H. Sneath: The application of computers to taxonomy. In:Journal of general microbiology. 17(1), 1957, S. 201–226.

A: According to Oxford Dictionary the word cluster is derived from the Old English word 'clyster' and was "probably related to clot [or clott]" and is derived from the Germanic 'klotz'.
