From ᾰ̓πό (ăpó), used as a prefix.

ᾰ̓πο- • (ăpo-)

Indicating movement: away, from, off
ᾰ̓ποβαίνω (ăpobaínō, “step off”)
Indicating breaking one part from another: un-, asunder, apart, off
ᾰ̓ποτέμνω (ăpotémnō, “cut off”)
Indicating ending or finishing, or almost like the negative ᾰ̓- (ă-, “not”), especially in adjectives
ᾰ̓πᾰλγέω (ăpălgéō, “put away sorrow for”), ᾰ̓πόσῑτος (ăpósītos, “having eaten nothing”)
back, again
ᾰ̓ποδῐ́δωμῐ (ăpodĭ́dōmĭ, “give back”)
Simply emphasizing the meaning of the verb
because of, owing to

Ancient Greek