'nu-bar' originates from a combination of Greek and English: the element 'nu' comes from Greek, specifically the letter 'nu' (ν), and 'bar' comes from English (from Old French 'barre'/'bar' ultimately meaning a mark or rod) used in scientific notation to denote a barred symbol.

'nu-bar' changed from the notation 'ν̄' used in printed physics and the spoken phrase 'nu bar' and eventually became represented in text as the hyphenated English form 'nu-bar'.

Initially it referred to the Greek letter 'nu' with a bar marking (i.e., the barred symbol 'ν̄'); over time it came to be used specifically to name the particle 'antineutrino', the antiparticle of the neutrino.