The etimology of the words "apple" and the German "apfel" is the Wendish word "jab(o)lk(o)".
The evolution of the word goes: jabolko - jablk - ablk - abflk - apflk- apfl - apl (apple) The name for apple in modern Slovenian is still "jabolko" and this word derived from the Wendish word for a sphere "oblo" (je oblo ko = is spherical as).
Slovenians name the planet Earth "zemelska obla" (earth sphere)
The word "ball" also evolved from "oblo", "obel": obel - obl - bol