An Etymological Dictionary of Astronomy and Astrophysics

Of a molecular cloud or a nebula, the ratio of the volumes filled with matter to the total volume of the cloud.

Etymology (EN): Filling, from fill, from O.E. fyllan, from P.Gmc. *fullijan (cf. Du. vullen, Ger. füllen “to fill”), a derivative of adj. *fullaz→ full; → factor.

Etymology (PE): Karvand, → factor; pori, from por,
→ full.