Where does “24-hour clock” come from?

24-hour clock (English) comes from English clock, from Middle English clokke, from Middle Dutch clocke, from Old Dutch *clocca, from Proto-West Germanic *klokkā, from Medieval Latin clocca, from Old Irish cloc, from Proto-Celtic klokkos.

24-hour clock (English): A timekeeping convention in which the 24 hours of the day are treated as a single period rather than two sets of 12 hours, with the result that midnight is indicated as 00:00 (or sometimes 24:00), and the hours from 1:00 to 11:00 p.m. as 13:00 to 23:00

Definitions

  1. A timekeeping convention in which the 24 hours of the day are treated as a single period rather than two sets of 12 hours, with the result that midnight is indicated as 00:00 (or sometimes 24:00), and the hours from 1:00 to 11:00 p.m. as 13:00 to 23:00

Ancestry of “24-hour clock”, step by step

24-hour clock traces back through two separate lines of ancestry.

via English clock

StepLanguageWordMeaning
1EnglishclockAn instrument used to measure or keep track of...
2Middle Englishclokkeclock, timekeeping device
3Middle Dutchclockebell; something bell-shaped
4Old Dutch*cloccabell
5Proto-West Germanic*klokkābell
6Medieval Latincloccabell; travelers' cape, literally “a bell”, so...
7Old Irishclocbell; clock
8Proto-Celticklokkosbell
9Proto-Indo-Europeanklēg-

via English hour

StepLanguageWordMeaning
1EnglishhourA time period of sixty minutes; one twenty-fourth...
2Middle Englishhourehour; A time, occasion, or moment; A canonical...
3Old Frenchhourehour; time; moment to do something
4Latinhōrahour
5Ancient Greekὥραany defined period of time; season; climate
6Proto-Hellenic*worā
7Proto-Indo-Europeanwēr-true
8Proto-Indo-Europeanwer-to burn; to cover, heed, notice; squirrel
Every word from Proto-Indo-European klēg-Every word from Proto-Celtic klokkosEvery word from Old Irish cloc