Mānawenūz was the original Valarin name for Manwë. It meant "Blessed One, One (closest) in accord with Eru".
J.R.R. Tolkien, Christopher Tolkien (ed.), The War of the Jewels, "Part Four. Quendi and Eldar: Appendix D. *Kwen, Quenya, and the Elvish (especially Ñoldorin) words for 'Language': Note on the 'Language of the Valar'"