Re: Hyder Smith b. 1858 Hardy Co. WV d. 1938 Moorefield, WV
A bit of a mystery, eh? it looks to me that Eunice is in the household of Margaret Ann Smith age 39 in 1850 Hardy Co VA.
There is also a Daniel Smith age 1, and it appears to be the same Daniel Smith in 1870 in Hardy Co WV with Una E Smith.
Although it's unknown who the husband of Margaret Ann Smith of 1850 Hardy Co VA is, note that Cuthbert Smith is living right next door with an aged John Smith in his household (88 years old). That would seem to point to John M Smith b c 1773 in Frederick Co VA whose wife was Eunah.
In 1840 Pendleton Co VA, there is a Daniel Smith living next door to Cuthbert, looks like they are both about the same age range. Theorizing that thisDanielwas married to Margaret Ann and Eunice is their daughter named after Daniel's mother. Again, theory.