Why are glass marbles also called Ollies?

Marbles became very popular during the Victorian age. At that time many children from poorer families could not afford to buy glass marbles. So, many poorer children used salvaged metal ball bearings, which had become increasingly available because of industrialisation. These ball bearings were referred to by many children as 'Ballies' or "Bollies.' I assume that the letter 'B' was simply dropped, for differentiation purposes, when the name was extended to include glass marbles.