An Etymological Dictionary of Astronomy and Astrophysics

Of a number, not divisible by two.
A function such as f(x) with the
property that f(-x) = - f(x) for any value of x; e.g. sin(x).

Etymology (EN): From M.E. odde, from O.N. oddi “odd (number).”

Etymology (PE): Tâq, related to tak “single, alone”, from Mid.Pers. tak, tâg “single, alone,” maybe related to tâi, tâ “unit, piece.”