Iliad
Refers to stories about tragic love in times of conflict
You know how we use "odyssey" from Homer's Odyssey to refer to long and winding journeys?
How about a term based on Homer's other epic?


Bathsheban
A story theme revolving around a bathing beauty who gets captured by a voyeur
This refers to an account in the Bible verse 2 Samuel 11 in which David (of "and Goliath" fame) spies on a maiden called Bathsheba who is bathing, and then he sends his servants to get her and...let's just say it doesn't end well for her.
I've seen this folktale theme referred to as "the Swan Maiden" or "the Animal Bride", and I even once referred to it as "the Bathing Bride".
Eventually, I settled on "Bathsheban" because it sounds cooler than these rather mundane terms, and also works very well as a play on words due to the first four letters of her name.


Oisin effect
The feeling that your entire world is changing before your very eyes
Derived from the Irish legend of Oisin, in which he travels to the Land of Eternal Youth and then returns home...only to find that 300 years have passed


Mermaid's Corpse
Sea foam
In the original Little Mermaid story by Hans Christian Andersen, the nameless main character dies and turns to sea foam.
Because of this, I have come to think of the foam of the ocean waters as the remains of dead mermaids.
 
 
Lafcadian
Taking interest in cultures other than yours
Comes from Lafcadio Hearn, an Irish-Greek writer who lived his later life in Japan, where he would become one of the first great interpreters of Japanese cultural things to the Western world.
His book Kwaidan:  Stories and Studies of Strange Things, is based on Japanese folktales.


Giant-killer
A severe thunderstorm
Derived from Norse mythology stories about Thor (the god of thunder) slaying malevolent giants.


Like a Hindu god
 Able to multitask at an expert level
Refers to how many Hindu deities have more than one pair of arms


Midgard
A term for Denmark, Norway, Sweden, and Iceland collectively
Refers to the realm of humans in Norse mythology
(Here, refers to the lands from whence the Vikings came, as well as the country that contributed the literary Eddas)


The Yuki-Onna's kiss
A terrible but not too bad snow event
Derived from the snow phantom of Japanese mythology


Fimbulwinter
A severe blizzard
Fimbulwinter, the first sign of Ragnarok, consists of three harsh winters with no summer in between.


King of the Heavens
A man who has many female love partners
In practically every mythology, the top god/ruler of the heavens is always philandering with maidens


Coyote
To cheat or swindle
References Coyote's role in Native American myths as the trickster


Fruit of Knowledge
Increased awareness of a truth that has gone unseen
After Adam and Eve ate the Fruit of Knowledge of Good and Evil, they suddenly were aware of their anatomy and tried to cover up.