The stealth rework itself was also inspired by it.
The same exclamation mark appeared when Rengar used Thrill of the Hunt to warn his enemies he is nearby, before it was replaced by a unique Icon resembling his eyes peeking through darkness during the Assassin update.
Her current title, "Agony's Embrace", was the name of her old ultimate.
Her ultimate was also named "Widowmaker" during early reveals, which was her original title.
Allure was formerly called "Lust Dust" in early reveals.
Evelynn had only manifested into her physical form a few centuries ago, as she has evolved from the the Rune Wars- which is fairly young for a demon.
Evelynn's entirely feminine form is not indicative for any fixed appearance, she can alter herself in different ways. However Evelynn doesn't do so on a whim, as her current form is something she spent decades of trial and error to make perfect.
Evelynn has killed the patron and matron of House Vayne of Demacia. Their daughter, Shauna Vayne has dedicated her life to finding and destroying monsters. Searching for the demon to exact her revenge.
Like Tahm Kench, she is classified as a demon, and as both are demons they seem to know each other based on their biography and Evelynn's quotes.
"So how are you, River King? I see you haven't missed a meal."
"I like your style, Kench, but stay out of my territory."
↑V. Orel, A handbook of Germanic Etymology, pp. 2, 4-5, 31