What is the etymology of “Laconia”?

Well, Chad Turner, Frisk and Chantraine are on the internet…

Frisk (Lakōn): Krahe, in Indogermanische Forschungen 57:119, relates the name as suspected Illyrian to Lacinium, a promontory in Southern Italy, and Juno Lacinia.

Chantraine (Lakedaimōn): Etymology unknown. There have been unsuccessful attempts to use the gloss in Hesychius “lakedama: bitter water made in the sea [poured out in salt flats] which the peasants of Macedonia drink”. […] Szereményi, Glotta 38 (1960): 14–17 invokes the Mycenaean anthroponym Rakedano, dative Rakedanore, which he reads as Lakedanōr “Laked-man”, which would yield the same first part of the compound Laken-daimōn: ingenious, but still dubious. One can also interpret Lakedaimōn as an indigenous prehellenic term.