Ingoldo was the amilessë of both Finarfin and his son Finrod Felagund. The name means simply "the Ñoldo, one eminent in the kindred". It was usually used by Finrod's brothers and sister, who esteemed him. As Finrod came to Middle-earth and had a good relations with the Atani, this name spread. Thus it was used as a given name in Númenor, and later also in Gondor, where it was changed to Ingold.
Other versions of the legendarium
In earlier texts, Tolkien considered this name as the mother-name of Fingolfin, meaning that he came from both the kin of the Ingar (Vanyar) and the Noldor, while the mother-name of Finarfin was Ingalaurë. Tolkien also considered to change Fingolfin to Ingolfin, so this would be the Sindarized form of his mother-name, but soon all this conception was discarded.
- J.R.R. Tolkien, Christopher Tolkien (ed.), The Peoples of Middle-earth, "XI. The Shibboleth of Fëanor", "Notes", p. 360
- J.R.R. Tolkien, Christopher Tolkien (ed.), Morgoth's Ring, "Part Three. The Later Quenta Silmarillion: (II) The Second Phase: Of the Silmarils and the Unrest of the Noldor", Notes, p. 265
- J.R.R. Tolkien, "Words, Phrases and Passages in Various Tongues in The Lord of the Rings: Eldarin Roots and Stems", in Parma Eldalamberon XVII (edited by Christopher Gilson), p. 118