Gerund form functioning as a noun meaning the act of causing affection.
Definitions
The act or process of making someone or something beloved. His constant endearing of the audience eventually won their hearts.
endeargerund / present participle Used attributively to describe something that inspires affection (e.g., an endearing smile).
Definitions
Inspiring affection, love, or fondness; charming. The toddler gave an endearing grin that melted everyone's heart.