Is this an existing function?

If the ordering of the tuples is irrelevant, then yes, this is an important construction! Your input is the set of edges in a graph, and your output is the partition of that graph into connected components.

Concerning the name of the function, for example, the NetworkX library literally calls it connected_components().

If the ordering within and among all the tuples must be observed, then I guess you have an edge-ordered directed graph, and you want an ordered partition of vertex-ordered components. Basically the same thing, but more work; and I don't know if that function has a well-known name.