"apple of one's eye" 這壹詞最早出現於聖經裏：詩篇17:8：Keep me as the 'apple of the eye' , hide me under the shadow of thy wings;《申命記》三十三章的第十節：In a desert land he found him, in a barren and howling waste. He shielded him and cared for him; he guarded him as the 'apple of his eye'。
跟東方壹樣，在西方，人們也壹直都把蘋果視為壹種吉祥的水果。不是還有另壹句英文諺語："An apple a day, keeps doctor away"。所以"apple of one's eye"就是指「珍貴的東西」，也就常被引申為「珍愛的人或物」。
所以說You are the apple of my eye，意思就是指說：妳是我的摯愛，或是同等意思。