Is it known who first associated the Beast of Revelation with the Antichrist, and when? I am NOT asking the similar question "Why is the second beast of Revelation called the Antichrist?" Rather, my question is specifically, when was the first connection made between the two--equating one of the beasts in Revelation with THE Antichrist--and if known, who made the connection?

I am looking for a firm connection here. For example, Justin Martyr spoke of "the man of apostasy, who speaks strange things against the Most High". This is a clear reference to Revelation 13, but he never uses the title "Antichrist".

Does Irenaeus, writing between about 175 and 185 AD make the connection? If so, was there someone before him?
Reading the new testament texts within a systematic eschatology, readers could conceivably equate the 'antichrist' of the Johannine epistles with either of the beasts from the Revelation, or the 'man of lawlessness' from Paul, but this is purely reader inference; such connections are not made explicit within these individual texts (e.g. the author of 1 John does not make any verbal references that he has 'the beast' of Revelation in mind).

The earliest known use of the term 'antichrist' outside of the Johannine epistles comes from a letter from Polycarp, a student of John, to the church in Philippi. He wrote some ten or fifteen years after the Johannine epistles, but clearly is working within the teaching represented by 1 and 2 John. With corroborating material from Polycarp's fellow student of John, Ignatius, the context of each of these three men's letters highly suggests 'antichrist' was originally used to describe some manner of docetism.

That I can find, Irenaeus was the earliest one to explicitly connect 'antichrist' to the beast of Revelation. In his Against Heresies, written around 180 AD, Irenaeus says the following:

Such, then, being the state of the case, and this number being found in all the most approved and ancient copies, and those men who saw John face to face bearing their testimony; while reason also leads us to conclude that the number of the name of the beast, according to the Greek mode of calculation by the the letters contained in it, will amount to six hundred and sixty and six. (5.30.1)
We will not, however, incur the risk of pronouncing positively as to the name of Antichrist for if it were necessary that his name should be distinctly revealed in this present time, it would have been announced by him who beheld the apocalyptic vision. For that was seen no very long time since, but almost in our day, towards the end of Domitian's reign. (5.30.3)

Here 'the name of the Antichrist' is identified with some passage of 'the apocalyptic vision'. Irenaeus is talking about the 'name of the beast' from Revelation 13.16-18. Contextually, Irenaeus is clearly talking about the first beast, from the sea, not the second beast, from the earth.
Other points in this chapter of Irenaeus' book also equate 'the Antichrist' with the first beast of Revelation, such as applying Revelation 13.5 or 17.8 to him.