Where does “twenty-four-hour clock” come from?

twenty-four-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.

Ancestry of “twenty-four-hour clock”, step by step

twenty-four-hour clock traces back through 3 separate lines of ancestry.

via English clock

Step	Language	Word	Meaning
1	English	clock	An instrument used to measure or keep track of...
2	Middle English	clokke	clock, timekeeping device
3	Middle Dutch	clocke	bell; something bell-shaped
4	Old Dutch	*clocca	bell
5	Proto-West Germanic	*klokkā	bell
6	Medieval Latin	clocca	bell; travelers' cape, literally “a bell”, so...
7	Old Irish	cloc	bell; clock
8	Proto-Celtic	klokkos	bell
9	Proto-Indo-European	klēg-	—

via English hour

Step	Language	Word	Meaning
1	English	hour	A time period of sixty minutes; one twenty-fourth...
2	Middle English	houre	hour; A time, occasion, or moment; A canonical...
3	Old French	houre	hour; time; moment to do something
4	Latin	hōra	hour
5	Ancient Greek	ὥρα	any defined period of time; season; climate
6	Proto-Hellenic	*worā	—
7	Proto-Indo-European	wēr-	true
8	Proto-Indo-European	wer-	to burn; to cover, heed, notice; squirrel

via English twenty-four

Step	Language	Word	Meaning
1	English	twenty-four	The cardinal number immediately following twenty-three and preceding twenty-five

Every word from Proto-Indo-European klēg- →Every word from Proto-Celtic klokkos →Every word from Old Irish cloc →