Eight
Old English ehta, eahta, of Germanic origin; related to Dutch and German acht, from an Indo-European root shared by Latin octo and Greek oktō .
wiktionary
From Middle English eighte, aught, eahte, ahte, from Old English eahta, from Proto-West Germanic *ahtō, from Proto-Germanic *ahtōu, from Proto-Indo-European *oḱtṓw.
Cognate with Scots aucht(“eight”), West Frisian acht(“eight”), Dutch acht(“eight”), Low German acht(“eight”), German acht(“eight”), Norwegian åtte(“eight”), Swedish åtta(“eight”), Icelandic átta(“eight”), Latin octo(“eight”), Ancient Greek ὀκτώ(oktṓ), Irish ocht(“eight”).
See ait.
etymonline
eight (adj., n.)
"1 more than seven, twice four; the number which is one more than seven; a symbol representing this number;" late 14c., eighte, earlier ehte (c. 1200), from Old English eahta, æhta, from Proto-Germanic *akhto (source also of Old Saxon ahto, Old Frisian ahta, Old Norse atta, Swedish åtta, Dutch acht, Old High German Ahto, German acht, Gothic ahtau), from PIE *okto(u) "eight" (source also of Sanskrit astau, Avestan ashta, Greek okto, Latin octo, Old Irish ocht-n, Breton eiz, Old Church Slavonic osmi, Lithuanian aštuoni). From the Latin word come Italian otto, Spanish ocho, Old French oit, Modern French huit. For spelling, see fight (v.).
Meaning "eight-man crew of a rowing boat" is from 1847. The Spanish piece of eight (1690s) was so called because it was worth eight reals (see piece (n.)). Figure (of) eight as the shape of a race course, etc., attested from c. 1600. To be behind the eight ball "in trouble" (1932) is a metaphor from shooting pool. Eight hours as the ideal length of a fair working day is recorded by 1845.
