In a way that causes no physical or emotional pain or difficulty; easily and without suffering.
From 'pain' (from Latin 'poena' meaning punishment) plus the suffix '-less' (without) plus '-ly' (adverb marker). The combination literally means 'without pain, in a manner without pain.'
Interesting fact: some people are actually born without the ability to feel pain due to a rare genetic condition—while it sounds lucky, it's actually dangerous because pain warns us when something is wrong with our bodies! Painlessness isn't always good.
Complete word intelligence in one call. Free tier — 50 lookups/day.