köken: From Middle Dutch speecsel, formed from older spekel by analogy with terms suffixed with -sel. The form spekel is from Old Dutch *spēkila, from Proto-Germanic *spaiklō. From the same root as spuwen. Cognate with German Speichel.
köken: From Byzantine Greek σάλιον (sálion), from an unattested *σιάλιον (*siálion, “saliva”) with elision of -ιά- (-iá-) > -ά- (-á-), itself a diminutive formation from Ancient Greek σίαλον (síalon, “spittle, saliva”), perhaps with some phonetic conflation from σίαλος (síalos, “fat pig; grease”).
From Mongolic silükei ~ šilükei "saliva", from Proto-Mongolic *sil- (“saliva; mucus; wet”). Note that the s-/š- variation at the beginning (compare шеләгәй) go back to the diachronous variation within Mongolic. Cognate with Tuvan шилегей (şilegey), Khakas сілегей (sìlegey), Crimean Tatar silekiy, Southern Altai шилекей (šilekey), Kazakh сілекей (sılekei, “saliva”), etc.