byway

noun

1. A road or track not following a main route; a secondary or minor road or path.

   “Near-synonyms: back road, back street, back lane”

   “Although some of its individuality has been lost, this railway byway in North Essex still retains its charm, and is well worthy of exploration by railway enthusiasts.”

2. A road that is not frequently travelled.
3. (broadly)a little-known or arcane field of study or detail.

   “Though his account of written communication over the past 5,000 years necessarily has a powerful forward momentum, his diversions down the fascinating byways of the subject are irresistible ...”