From ὖ (û) with a rough breathing. The aspirated form ὗ is attested in ancient Greek grammarians' works, such as Steph.Gramm. and Myrin., as well as in inscriptions (e.g., AP9.385.20, AP11.67.1). The aspirated pronunciation is supported by comparisons with Latin (e.g., the letter Y in the name Hypsaeus) and Coptic, where it appears as "he." This form is likely an early distinction, as noted in LSJ and Triantafyllidis' lexica.
ὗ • (hû) n (indeclinable)
This rare form, ὗ, appears in ancient Greek texts and inscriptions for phonetic distinction, primarily as a less common alternative to the standard smooth-breathing ὖ. According to LSJ and Triantafyllidis, ὗ may have indicated a different historical pronunciation, especially in formal or poetic contexts. Most notably, the aspirated form is linked to the pronunciation of words starting with υ, such as ὕαλος and υἱός.
In Liddell-Scott-Jones Greek-English Lexicon (LSJ), ὗ is noted to appear in a few specific cases, including in AP9.385.20 and AP11.67.1, where it is indicated with rough breathing. The form may have been used in certain dialects or inscriptions to differentiate the pronunciation of υ from its smooth-breathing counterpart. The lexicon also notes parallels in Latin (Hypsaeus) and Coptic usage (he), which suggest an earlier, now rare, phonetic distinction.
In the M. Triantafyllidis Dictionary of Standard Modern Greek, it is noted that υ was pronounced with a rough breathing in ancient times, particularly at the beginning of words. Over time, the rough breathing was dropped in most forms, but it retained significance in specific dialects and formal speech. The aspirated form continued to indicate a historical distinction that persisted in certain written forms.