Where did the term "fickle mistress" come from?

As you can see here, the phrase "fickle mistress" is quite common, especially in personifying something (life, love, time, etc). But I can't seem to find any real source on how far back it goes and/or where it came from. Neither the OED nor Etymonline seem to have anything as far as I can see.

Sorry if I've overlooked something obvious. Any help is appreciated with this!

At first I thought it dated to Shakespeare, because I found this reference:

Timon, in the last act, is followed by his fickle mistress, &c. after he was reported to have discovered a hidden treasure by digging.

The Plays of William Shakespeare 17th volume

Then, I found an ode written by Sir Thomas Wyatt (1503-1542) named The Lover recounteth the variable Fancy of his fickle Mistress

[emphasis is mine in both quotes]

As commented by Tonepoet, the usage "strongly suggests that the appeal of the word fickle may have been originally chosen here in part because of its alliterative appeal".

This is probably the earliest I will be able to find without access through a paywall. Of course, these are literal usages. I suppose that as long as men have had mistresses, they have complained about their fickleness.

The first figurative usage I found was...

Shew mercy to those that are shipwrecked, for the sea, like fortune, is a fair but fickle mistress.
The Republican (1825) -(supposedly attributed to Phocylides, appx. 540 BCE)

"Fickle mistress" is not a compound word as it is, it is a usage came in to being probably in 1745 (The Agreeable Companion; Or, The Universal Medley, &c, Volume 1) as the Google Books Ngram Viewer shows.

The etymology of 'fickle' and 'mistress' separately can be seen as follows:

From Online Etymology Dictionary

fickle (adj.) c. 1200, "false, treacherous, deceptive, deceitful, crafty" (obsolete), probably from Old English ficol "deceitful, cunning, tricky," related to befician "deceive," and to facen "deceit, treachery; blemish, fault." Common Germanic (compare Old Saxon fekan "deceit," Old High German feihhan "deceit, fraud, treachery"), from PIE *peig- (2) "evil-minded, treacherous, hostile" .

Sense of "changeable, inconstant, unstable" is from c. 1300 (especially of Fortune and women). Related: Fickleness. Fickly (c. 1300) is rare or obsolete. Also with a verb form in Middle English, fikelen "to deceive, flatter," later "to puzzle, perplex," which survived long enough in Northern dialects to get into Scott's novels. Fikel-tonge (late 14c.) was an allegorical or character name for "one who speaks falsehoods.

mistress (n.) early 14c., "female teacher, governess," from Old French maistresse "mistress (lover); housekeeper; governess, female teacher" (Modern French maîtresse), fem. of maistre "master" (see master (n.)). Sense of "a woman who employs others or has authority over servants" is from early 15c. Sense of "kept woman of a married man" is from early 15c.

It is from an aria in the Third Act of Rigoletto by Giuseppe Verdi (the libretto was written by Francesco Maria Piave):

La donna è mobile
Qual piuma al vento,
muta d'accento
e di pensiero.

Sempre un amabile,
leggiadro viso,
in pianto o in riso,
è menzognero.

The standard English translation runs as follows:

Woman is fickle
Like a feather in the wind,
Her voice keeps changing,
And so do her thoughts.

Always a lovely,
Pretty face.
In tears and in laughter
Equally untrue.

It's one of Luciano Pavarotti's favorite concert pieces:

https://youtu.be/IjVJ1lIoUBw