[nettle]

Here is my sumuni worth of what I know about the two places - going back to the sixties.

Dagoretti Corner: for Dagoretti see one of the post above. Note that there are other places that carry Dagoretti as an adjective: Dagoretti Market and Dagoretti Centre. (Hope no one will say they mean The Great Market or The Great Centre!) Most likely this trend could have influenced the name. Especially since Corner was the farthest end of the area considered Dagoretti.
Up to 1969, the Nairobi city proper went up to Corner- all the area from Dagoretti Corner westwards was peri-urban. The popular name of Corner was Karandi-ini. Most of this land was lorded over by the Wanyee Family.

I mention this to point out that after the demarcation, the area was owned by distinct prominent families - hence the many names characteristic of the area and Dagoretti in general.