The term Rayyan Haya' is a combination of two Arabic words; Rayyan ريَّان is the name of one of the doors of Paradise, according to Islamic tradition.
Lexically, the word ‘Rayyaan’ means well-watered, lush, succulent, pretty, sated with drink, etc. It is commonly used as an adjective for something positive, e.g. some who has a lot of knowledge would be referred to as ‘Rayyaan bil Ilm’.
Haya' هيا may be translated as modesty, shyness, self-respect, bashfulness, shame honor, humility etc. The original meaning of Haya refers to a bad and uneasy feeling accompanied by embarrassment, caused by one's fear of being exposed for some unworthy or indecent conduct.
Islamically, Haya' is an attribute which encourages believers to avoid anything distasteful.