part of a province closest to the capital
Archaic administrative term referring to the area of a province nearest to the capital, contrasted with 道の後 (the farthest part) and 道の中 (the middle part).
Under the ritsuryō system, 道の口 referred to the area of a province closest to the capital.
Compound of 道 (michi, 'road; administrative circuit') + の (no, possessive particle) + 口 (kuchi, 'mouth; entrance'). The term is based on the spatial metaphor of a road leading from the capital, with the 'mouth' being the nearest section.