Hey there! I've answered this before!

Here's the answer with a bit more elaboration.

Dildoes were indeed in semi-common use and probably general knowledge by the 1600s. The first reference to dildoes in western literature, indeed, may date all the way back to the 1500s, in Pietro Aretino's 'Secret Life of Nuns' where the narrator recounts:

Nana: Then he uncovered his basket and set it on the table. At once a roar of laughter arose that sounded like thunder. No sooner were those fruits of paradise seen than the hands of both sexes, already engaged with one anothers thighs, tits, flutes and bags, lunged for them with the dexterity of pickpockets… They were glass fruits made in Murano near Venice to look like a prick. [But I was too innocent to realize that at the time].

Though they are not called dildos as of yet–that word entered the English language about 1590, likely from the Italian deletto, meaning delight, and, perhaps originating from the works of Aretino. This is the etymology as I've been able to sketch it out so far.

Dildo was definitely used in the modern sense by the sixteenth and seventeenth centuries. Compare Rochester's poem, Signor Dildo in 1673

[G]o thither to make your Selfes Sweet,

By Buying of Powder, Gloves, Essence, or Soe

You may Chance get a Sight of Signior Dildo.

You’l take him at first for no Person of Note

Because he appears in a plain Leather Coat:

But when you his virtuous Abilities know

You’ll fall down and Worship Signior Dildo.

Or, even earlier, Nashes Dildoe dated around 1620, wherein the male protagonist leaves his partner unsatisfied and she takes out “my little dildo…that bendeth not / and stands as stiff as he were made of steele.” She says that her glass friend “refreshes her well / and never makes my tender belly swell [with a child].”

The 'fine dog with the hole in his head' likely refers to the fact that the higher-quality dildoes were supposed to shoot fluid out of them, it was seen as essential to women's pleasure. See this example of a high end 17th century dildo that had this feature: https://imgur.com/43G7nab There are a number of engravings (that I don't have on me right now) that show women's maids helping them with the pump action of these dildos.

However, the fine dog could likely refer to a penis as well, it's not too far afield from some of the bawdy songs I've read. I've written on the history of dildoes a number of times and you can find some of them here..