before 1000;Middle Englisheighte,Old English (e)ahta; cognate with Dutchacht,Old Saxon,Old High Germanahto (Germanacht), Old Norseātta,Gothicahtau,Latinoctō,Greekoktṓ,Old Irishocht,Welshwyth,Bretoneiz,Tocharian Bokt,Lithuanianaštuonì,Albaniantetë, Armenian uth,Persianhasht,Sanskritaṣṭáu; apparently an old dual in form, but not clear of what
O.E. eahta, æhta, from P.Gmc. *akhto(u) (cf. O.N. atta, Ger. acht, Goth. ahtau), from PIE *okto (cf. Gk. okto, L. octo, O.Ir. ocht-n, Bret. eiz, Skt. astau, Avestan ashta). Klein calls it "an old dual form, orig. meaning 'twice four.' " 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. To be behind the eight ball "in trouble" (1932) is a metaphor from shooting pool.