From Greek 'diabolos' (slanderer) — 'dia-' (across) + 'ballein' (to throw). The same 'throw' root gave us 'ballistic.'
The supreme spirit of evil in Christian and Jewish theology; a wicked or cruel person; a mischievous person.
From Old English deofol, from Latin diabolus, from Greek diabolos (διάβολος, slanderer, accuser, one who throws across), from dia- (across, through) + ballein (to throw). Greek ballein derives from PIE *gwel- (to throw, to pierce, to reach) — the same root that produced English ball (something thrown), ballistic, problem (thrown before you), symbol (thrown together), and parable (thrown alongside). In the Septuagint — the Greek translation of the Hebrew Bible — diabolos translated Hebrew satan (adversary, accuser). The theological identification of Satan and the devil fused the Hebrew adversarial
The devil is literally 'one who throws across' (dia- + bállein). The word 'symbol' comes from the same root: 'syn-' (together) + 'bállein' (to throw) — something 'thrown together' as a sign. A 'problem' is something 'thrown before' you (pro- + bállein). And 'ballistic' is from 'bállein' too. The Greek verb 'to throw' is everywhere in English.