Note 232 — SOAP.
William Johnston translation
It is beyond all doubt that the words sapo and σάπων were derived from the German sepe, which has been retained in the Low German, the oldest and original dialect of our language. In the High German this derivation has been rendered a little more undistinguishable by the p being changed into the harder f. Such changes are common, as schap, schaf; schip, schiff, &c.