Containing lots of meat; also means substantial, interesting, or full of important content (like a 'meaty' discussion).
From 'meat' (Old English 'mete,' originally any food) plus '-y' suffix. The literal sense came first (1400s), the figurative sense (meaning 'substantial') developed in the 1900s.
The metaphorical use of 'meaty' is clever because the brain unconsciously links 'meat = substance, nutrition, weight'—so a 'meaty question' sounds more serious and important than a 'thin' or 'light' one, which is pure psychology.
Complete word intelligence in one call. Free tier — 50 lookups/day.