colostra.

Of uncertain origin; proposed derivations include: * From Proto-Indo-European *ḱwel-, common to Old English hwylca (“varix”), hwelian (“to suppurate”) and Lithuanian švelnùs (“soft, smooth”). * From Proto-Indo-European *ḱewH- (“to swell”), thereby cognate with Latin cavus (“hollow”), Old Norse hváll (“round hill”) and Armenian շեղջ (šeġǰ, “heap, pile”). * Assuming an earlier *corostra which underwent dissimilation, akin to Sanskrit शर (śara, “sour cream”) and शरस् (śáras, “film on cooked milk”), from Proto-Indo-European *ḱorh₂os (“decay, rot > sour milk”), from the root *ḱerh₂- (“to break, decay”), thereby cognate also with Proto-Celtic *kerati (“to fall”), Ancient Greek κεραΐζω (keraḯzō, “to ravage, plunder”), and Sanskrit शृणाति (śṛṇā́ti, “to crush”). * Related to colōr (“color”) (< *"cover"); however, this is semantically and morphologically difficult.