Headachiest

Part of speech: adjective

Definitions

1. Most likely to cause difficulty, frustration, or a throbbing pain in the head
2. Most vexing, bothersome, or prone to creating stress and mental strain
3. Most problematic or irritating in nature, causing the greatest amount of distress

Etymology: "Headachiest" is the superlative of "headachy", which is itself formed from "headache" and the suffix "-y", meaning "full of" or "characterised by". The suffix comes from Old English "-ig", which passed through Middle English "-y" to the form used today, so the adjective is a simple combination of an old noun and an old English ending. "Headache" is a compound of "head" and "ache". "Ache" descends from Old English "æce", and the "head" half traces back to the Proto-Germanic word for the top of the body, which is far older than the English language itself. Put together, "headache" describes pain in the head, and "headachy" describes something that brings on or resembles that pain. The superlative adds "-iest" to "headachy" in the usual way for two-syllable adjectives ending in "-y", changing the "y" to "i" before the ending. It describes the thing that causes the most head pain of any in a group being compared.