Gday,
The GOSPELS themselves were completely unknown in the 1st century.
But, in the 2nd century we start to see some references to written Gospels - WITHOUT author's names. The names were only attached in late 2nd C., probably by Irenaeus.
Apology of Aristides, 138-161CE :
And it is said that God came down from heaven, and from a Hebrew virgin assumed and clothed himself with flesh; and the Son of God lived in a daughter of man. This is taught in the gospel, as it is called, which a short time was preached among them; and you also if you will read therein, may perceive the power which belongs to it.
This is obvious evidence of a written work which is specifically named "The Gospel" - but no name is given.
Furthermore, Aristides says this SINGULAR un-named Gospel was fairly NEW in the period 138-161 - clear evidence of the lateness of the Gospels, and the lateness of late naming.
Justin Martyr's 1st Apology, 150-160CE :
Ch. 66 : For the apostles, in the memoirs composed by them, which are called Gospels...
Justin Martyr's Dialogue with Trypho, 150-160CE, 3 references :
Ch. 100 : For I have showed already that Christ is called both Jacob and Israel; and I have proved that it is not in the blessing of Joseph and Judah alone that what relates to Him was proclaimed mysteriously, but also in the Gospel it is written that He said: 'All things are delivered unto me by My Father;' and, 'No man knoweth the Father but the Son; nor the Son but the Father, and they to whom the Son will reveal Him.'
This is all clear and obvious evidence of written works called Gospels - but no names given, even though Justin explicitly tells us what they were named ("which are called Gospels".) If Justin knew of any author's names he would CERTAINLY have given them.
The Acts of Peter, 150-200CE :
And Peter entered into the dining-hall and saw that the Gospel was being read, and he rolled up the book and said: Ye men that believe and hope in Christ, learn in what manner the holy Scripture of our Lord ought to be declared: whereof we by his grace wrote that which we could receive, though yet it appear unto you feeble, yet according to our power, even that which can be endured to be borne by (or instilled into) human flesh.
This is obvious evidence of a written Gospel - but no author's name is given.
The Treatise on the Resurrection, 170-200CE, 1 reference :
What, then, is the resurrection? It is always the disclosure of those who have risen. For if you remember reading in the Gospel that Elijah appeared and Moses with him, do not think the resurrection is an illusion.
This is obvious evidence of a written Gospel - but no author's name is given.
Hegesippus Fragments, c. 170CE :
With show of reason could it be said that Symeon was one of those who actually saw and heard the Lord, on the ground of his great age, and also because the Scripture of the Gospels makes mention of Mary the daughter of Clopas, who, as our narrative has shown already, was his father.
This is obvious evidence of a written Gospel - but no author's name is given.
It's clear that the Gospels were UN-NAMED until late 2nd century.
K.