Side (Side)
Essentially a connection of some kind: communication, contact, liaison; or any sort of attachment: physical, emotional, mechanical. It could be a bandage or sanitary pad, a cord or ribbon for tying, a ligament, a (chemical) bond… Part of a 1927 naming-spree and specific meaning not clear. Crosses Sihi, if that helps.
Siili (Siil) 
Hedgehog. The hedgehog has enjoyed modest success in Estonian martial-arts consultancy for their rather obvious observation that slicing rather than thwacking movements are more effective with flat weapons (cf. Kalevipoeg, Canto XII).
Sikupilli (Sikupill)
Bagpipes, lit. goat’s instrument. Named after nearby inn. What is a shopping centre today was a prison in the late-19th C and, prior to that, a hospital, but its damp limestone walls didn’t do the patients’ health much good, which didn’t seem to be an issue for the next occupants. It also had its own loop of railway passing in and out, allowing the reasonable deduction that the favoured occupation of, or rather for, convicts – breaking stones – was not to provide ballast for ships to which, being a port, Tallinn naturally lends itself, but stabilising railway lines. While local by-ways add weight to the argument, railway engineering takes it away (I bet nobody saw that one coming…), track ballast is smaller and lighter (see Pallasti). Well, it was a women’s prison... Renamed (1960-1990) as Killustiku during the Soviet occupation. One of a rock-based neighbourhood. See Tuha. Alternative name of Torupilli.