Although I am not a McOstrich I do have them in my tree.
A 2x great grand uncle, William Blair, married a Jessie McOstrich in Edinburgh 1865. Jessie was the daughter of Alexander McOstrich and Janet Stoddart. Alexander was born in London in 1800 son of Robert and Martha McOstrich.
These McOstrichs only seem to have lasted briefly as there were three girls and one boy who died in 1865 unmarried.
I checked only 4 McOstrich girls married between 1855 and 2000,no McOstrich births occurred before 1837 and only 8 McOstrich deaths are recorded in Scotland