Traditional 發 showed a bow releasing — shooting forth, launching, issuing. Simplification merged it with 髮 'hair' (fà), so one character now covers both firing rockets and bad haircuts, distinguished only by tone.
发现 discover, 发烧 run a fever, 出发 set out, 发红包 send red envelopes. 发财 'to shoot forth wealth' powers the New Year greeting 恭喜发财 — 'congratulations, get rich'. Read fà: 头发 hair, 理发 haircut.
An arrow leaving the bow — SEND OUT, LAUNCH, DISCOVER.
The number 8 is lucky because bā rhymes with 发 fā 'get rich' — license plates and phone numbers stuffed with 8s auction for fortunes; one plate of 8s sold for millions of yuan.