cf. omicroniota 185, omicroniota 186. LSJ distinguishes between oi)su/ph, 'the grease extracted from sheep's wool', and oi)/sph (with its variant oi)spwth/), 'the dung that collects about the hinder parts of sheep or goats'. The similarity between the two words makes confusion between them -- in ancient and modern writers alike -- even more of a hazard than it would have been anyway. (Besides the present headword, which ought to have been oi)su/ph, see e.g. the variae lectiones in the Herodotus passage cited in n.1 below.)
[1] Herodotus 4.187.2: four-year-old Libyan nomad children have the veins on top of their head cauterized with it. (The present gloss is from the glosses there.)
[2] For this term see e.g. Aristophanes, Lysistrata 575 (where Henderson's note fails to make the necessary distinction).