All families

sandalum, santalum, = sandalwood.
(Ox)

sapo, = soap.
(also a name given by Central American Indians to a milky latex used to make chewing gum)
(ld, K3)

schiz, schizo, = to split, cleave.
(split, cleft, deeply divided)
-eus, = indicates material or colour or resemblance in quality.
(referring to the two-ranked spikes of sporangia)
(LS, BL, Le)

scrofa, = a breeding sow (supposed to be subject of the disease scrofula)
scrofulǣ, = a swelling of the glands in the neck, scrofula;
-ula, = diminutive.
(Ox, ld, BL)

selago, = a plant resembling the savin tree: the club-moss Lycopodium selago.
(SELAGO (q.v.))
(a name for medicinally-used juniper)
(the small leaves give members of the genus a superficial resemblance to the club moss)
(ld, Ox, Le, M)

sero, semen,= to sow, plant; propagating; a graft, scion, set, slip cutting;
-atus, = indicates possession or likeness;
phyllon, = a leaf.
(ld, BL, LS)

siphon, = a reed, straw, any tube;
(tube, pipe)
-ula, = diminutive.
(LS, BL)

sol, = the sun;
-anus, = belonging to, connected with, pertaining to, used to form adjectives from nouns, particularly from geographical and personal names.

solanum, = a plant called also strychnos, nightshade; (that deadly plant is a member of this genus)

Perhaps from solamen, soothing narcotic properties of some species.
(ld, BL, M, Le)

sphagnos, = a kind of fragrant moss.
(a Genus of mosses growing in boggy places, bog-moss, peat-moss)
(ld, Ox)

stictos, = pricked, branded: hence marked, spoted, dappled.
(pricked, toothed, spotted, dappled)
(LS, BL)

stilbe, = to shine, glitter, glisten.
(possibly referring to the silver-white flowers that appear to shine. The genus could also be named after the nymph Stilbe**; but ‘the alusion is not clear’.)
Stilbe, a nymph in Greek mythology, daughter of the Thessalian river-god Peneus and the nymph Creusa. By Apollo she became the mother of two sons, Centaurus and Lapithes, who gave his name to the Thessalian tribe, the Lapiths.
(BL, J, PG)