This is actually a great example of how to deal with a word’s etymology and meaning.
When the disciples could not exorcize the demon, Jesus responded, “O unbelieving (ἄπιστος) and perverse generation, how long am I to be with you?” (Matt 17:17).
After the exorcism, the disciples asked him why they could not perform the exorcism. Jesus replied, “Because of the poverty of your faith (διὰ τὴν ὀλιγοπιστίαν ὑμῶν). I tell you the truth, if you have faith the size of a mustard seed (ὡς κόκκον σινάπεως), you can say to this mountain, ‘Move from here to there,’ and it will move; and nothing will be impossible for you” (17:20).