I knew in my gut that "Sihu" was not the correct name. Thanks to Cousin Mary of Threading Needles in a Haystack the quandary has been resolved.
Kenny's great-great grandma's maiden name was.............Sihn.
Penmanship people, penmanship!!
Since Mary's response to my post we have found several census records for the Sihns as well as naturalization paper, listings in the NYC death index, and several entries in city directories. Those Sihns, who are of German origin, have been in the US for a long long time; since the 1860s.
Thank you again, Cousin Mary, thank you, thank you.