Killing a person intentionally and illegally, or in informal speech, doing something extremely well or with great intensity.
From Old English 'morthor' and Germanic roots meaning 'death.' The word has meant unlawful killing since before 1000 AD.
The slang 'murdering it' (doing amazingly) comes from the intensity of the original meaning—people metaphorically use the most intense words for things they care about deeply, revealing what a culture values.
Complete word intelligence in one call. Free tier — 50 lookups/day.