The following website has extensive information about the more than 700 slopes in Tokyo that have names: 「名前の付いた坂道」
The word 坂 means “slope”, and is pronounced, saka, though it can become zaka when used in combination, e.g. Nogizaka 乃木坂. By adding the kanji 道 (road, path, etc.), we get 坂道, which means “sloping road” or “hill road” and is pronounced sakamichi さかみち.
These roads acquire names for various reasons; Supein-zaka (Spanish hill) is so named for its “resemblance to a typically Spanish street” (source). Nearby is the famous Dogenzaka 道玄坂, known as “Love Hotel Hill” because of its high concentration of love hotels.
A google map of many of the named sakamichi in Tokyo’s 23 central wards:
And a slope map of Tokyo 坂道マップ, from the tokyo files – urban design: