Hi,
I might be way off track here and telling you something you already know

. If so, apologies.
But the term "land" could be referring to a building rather than an area of land.
So Back House could be part of the building possibly belonging to or built by McIllraith

Looking at the Valuation Rolls on Scotlands People , from 1850s onwards , there are several
MacIlwraiths who are proprietors /occupiers of property in Dailly.
There are
McIlraith listed on the 1881 Census at Dailly. Also
McIlluraith,
McIlraith and
McIluraith listed on the 1871. Phew , a few spelling permutations

Hope this has been of help,
Looby