Shinjuku (New Shuku → New Post Town)
The word 宿 shuku (宿場 shuku-ba “rest town”) was used in the Edo Period to refer to post towns on the highway system connecting various feudal domains. When a certain daimyō built his lower residence in the area, a new post town was created on the Kōshū Kaidō post road and named “new post town.”
The daimyō family who lived here was called 内藤 (Naitō), so the name of the town became Naitō–Shinjuku (New Shuku Naito). The name Naito-Shinjuku persisted until the 1920’s.
As a post town, there would have been many places to drink and get laid. Modern Shinjuku isn’t much different… except that the Tokyo Municipal Government is also based there. Awwwww yeah.