all-important

The compound "all-important" is a relatively modern English formation, emerging in the 19th century. It follows a classic Germanic compounding pattern where an intensifier ("all") is prefixed to an adjective ("important") to create a superlative or emphatic sense. The logic is transparently literal: something that is "entirely important" or "important in every respect" is therefore of the utmost, vital significance. While "important" itself has a Latinate origin, its combination with the native English intensifier "all" creates a hybrid term whose meaning is immediately accessible.

Structure: all (entirely) + important (significant) - all: From Old English eall, meaning "entire, whole, every." In this compound, it functions as an intensifying prefix, meaning "completely, entirely." - important: From Medieval Latin importare (to be of consequence), via Italian importante. In this compound, it functions as the core adjective meaning "of great significance or value."