I have a distant connection to the Cohenno family; my father's sister married a Cohenno. I don't know much about this, but there are a couple of references that might be interesting to dig into.
First there is the record of the name change of Fred Newell Simmons (Fred would have been 19 years old at this date):
Date of Decree.: July 16, 1890
Original Name.: Fred Newell Simmons,
Name Decreed.: Fred Newell Cohenno,
Residence.: Stoughton.
I have no idea what the Norfolk County probate records would show--perhaps nothing more than this--but it might be worth a look.
Second, there is an 1877 article in the New York Times about a diamond robbery. A Boston Diamond merchant, identified only as H. Cohenno, was robbed of his entire inventory by his partner. It was a very substantial loss and the article concludes that the robbery "ruins Cohenno financially, and throws out of employment a number of expert diamond cutters and polishers."
http://query.nytimes.com/gst/abstract.html?res=9F0CE6DA1F3BE...I have not yet tried very hard to look further into this, but the name Cohenno is now and was then very rare in the United States and it seems to me quite possible that this H. Cohenno was the Cohenno whose name Fred Newell Simmons took. A diamond merchant might well have come from Amsterdam, but I don't know if this one did.
It is my own hunch that Fred's immigrant Simmons Ancestor was Moses Simonson, who came to Plymouth in 1623 on the Fortune. That is nothing more than a guess. It would be interesting though, because it would be another Dutch connection.