Quenya form of "Morgoth"

[cesar.ewok]

I was wondering what the Quenya form of the name "Morgoth" was, since Melkor ("The Mighty-rising") has a different meaning (Morgoth = "Black Foe"). I took a look at Morgoth's Ring and found out:

"At the first three occurrences 'Morgoth' > 'Melkor', and at the end of the paragraph, after 'the violence of Morgoth', was added: 'for such was his name from that date forth among the Gnomes'; thereafter 'Morgoth' was retained. At the foot of the page my father noted: 'In more ancient form Moringotto'."
Morgoth's Ring, Part Three - The Later Quenta Silmarillion, The First Phase, Chapter 7 - Of the Flight of the Noldor

"[footnote to the text] By that name only was he known to the Eldar ever after. (In ancient form used by Fëanor it was Moriñgotho.) [Cf. the note added in LQ to QS §60 (p. 194), where the ancient form is Moringotto.]"
Morgoth's Ring, Part Three - The Later Quenta Silmarillion, The Second Phase, Of the Rape of the Silmarils

It doesn't really say if "Moringotto" is the Quenya form of the name - it is only said that it was a more ancient form (?). But apparently it is Quenya. Is it? I didn't also get this "Moriñgotho". What is it?