Q: Why are pictures hung and people hanged?
A: Both past tenses have been around for hundreds of years, but it’s been customary since the 16th century to use “hanged” for executions and “hung” for other meanings. Why? It’s an impossibly complicated history and takes up about a zillion (give or take) pages in the Oxford English Dictionary. I’ll summarize.
The story begins with several different verbs that were imported into different parts of England by different invaders who brought with them different forms of old Germanic tongues. In these different regions, different dialects evolved. Over the centuries, the English present tense (variously “hing,” “hang,” “heng,” “hong”) stabilized as “hang.”
Meanwhile, the past tense and past participle eventually stabilized as “hung,” a form popular in northern England that by the 16th century had spread to the south and superseded the many older forms for those tenses.
However, one old past tense and past participle, “hanged,” survived in a single sense: to put to death by hanging. The OED suggests that this archaic form was preserved in legal language, since it was used by judges to pronounce sentences in capital crimes.