all-day

The word "all-day" is a transparent English compound formed by combining two native Germanic elements. "All" derives from Proto-Germanic allaz, meaning "all, whole, every", which has a stable history in English. "Day" originates from Proto-Germanic dagaz, referring to the period of daylight and, by extension, a full 24-hour cycle. The compound's logic is perfectly literal, directly combining the sense of "entire" with "day" to create an adjective describing something that spans the complete duration of a day. This straightforward compounding process is a common and productive method in English for forming new descriptive terms.

Structure: all (entire) + day (a 24-hour period) - all: From Old English eall (all, every, entire). In this compound, it functions as an intensifier meaning "the whole of". - day: From Old English dæg (day, a 24-hour period). In this compound, it functions as the noun being modified.