From sill (“newly hatched young of fish, fry”) + -ock, cognate with Swedish dialectal sil (“the young of fish, fry”), Norwegian sil (“sand-eel”). More at sile.
"sillock." YourDictionary, n.d. Web. 17 August 2018. <http://www.yourdictionary.com/sillock>.
sillock. (n.d.). Retrieved August 17th, 2018, from http://www.yourdictionary.com/sillock