Henry George Liddell, Robert Scott, A Greek-English Lexicon

Υうぷしろんυうぷしろん , τό, indecl., twenty-third letter of the Formello abecedarium, IG14.2420, but twentieth of the Ion. alphabet: as numberal ύ = 400, but υうぷしろんͅ = 400,000. It is called τたうὸ ὖ by Pl.Cra.393d, Callias ap.Ath.10.453d (prob., the line ends τたうαあるふぁῦ, <τたうὸ> ὖ), IG22.2783.4 (iv B. C.), Hellad. ap. Phot.Bibl.p.530 B.; τό τたう᾽ ὖ or τό θしーた᾽ ὗ might be read in Achae.33.3 for τたうοおみくろんῦ υうぷしろん_ codd.Ath.; later τたうὸ υうぷしろん ψιλόν or τたうὸ ψぷさいιいおたλらむだὸνにゅー υうぷしろん (as name of the first letter of ὕαλος, υうぷしろんἱός, etc.), Theognost.Can.18, Sch. Ar.Pl.896, Ps. Hdn.Epim.116, 137, al.: so named to distinguish it from ἡ οおみくろん_ιいおた_ δίφθογγος, υうぷしろん and οおみくろんιいおた being pronounced alike in late Gr.; ὗ is aspirated in AP9.385.20 (Steph.Gramm.), 11.67.1 (Myrin.) cod.Pal.; the Coptic name