[1] Variations of the definition appear in the scholia to Aristophanes, Plutus [Wealth] 436, 737, 1054, as well as epsiloniota 184. The kotyle was a measure of volume/capacity (wet or dry), equating in present-day terms to around a quarter of a litre. A xestes was defined to be twice the size of the kotyle.
[2] The Etymologicum Gudianum attempts the same derivation for oi)=kos "house".
[3] LSJ s.v. kotu/lh 1 gives both as definitions of kotu/lh --- "small vessel, cup". This appears to be distinguishing the two senses, but is in fact a garbling of Aristonicus, De Signis Iliadis 22.494 (also in the scholia ad loc.): "pu/rnon and kotu/lh are used synonymously [in Odyssey 17.12] for a vessel for liquids." (Incorrect: the pu/rnos is a loaf of bread.)
LSJ defines xoi=nic as only a measure, and not a vessel, so it is not a parallel formation. While the kotu/lh was primarily a liquid measure (LSJ s.v. 3) and only occasionally a dry measure (LSJ s.v. 3b), the xoi=nic was a dry measure.
[4] LSJ s.v. 2: socket, especially hip-socket: Homer, Iliad 5.306. This sense derives, like "cup", from the primitive meaning "something hollow". The definition is taken from the scholia ad loc.
[5] This is a garbling of Aristotle fr. 1.7.63 Rose = Diogenes Laertius 9.53: what is so defined is the kaloume/nhn tu/lhn, "the so-called shoulder-pad". Protagoras' career is also mentioned in phi 610.