Šilasprogis

Perhaps a compound surn., the first stem of which is from Latv. sils (lit. ši̇̀las) „eglynas; tyrlaukis, dykynė and others“ (LVV III 839), see Heimm. For the second sand, cf. Latin surn. Sproģis ¹ and exploding Limm. surn. Vecsproģis, Sniķersproģis (ibid.).