我爱你在英文古语里怎么说？

I love thee.

thou 是主格，thee是宾格

I loveth thou.

应该是 I lufu ēow 采用于Old English
Main Entry: love
Pronunciation: \ˈləv\
Function: noun
Etymology: Middle English, from Old English lufu; akin to Old High German luba love, Old English lēof dear, Latin lubēre, libēre to please
Date: before 12th century
Main Entry: you
Pronunciation: \ˈyü, yə also yē\
Function: pronoun
Etymology: Middle English, from Old English ēow, dative & accusative of gē you; akin to Old High German iu, dative of ir you, Sanskrit yūyam you
Date: before 12th century
建议楼主买本韦氏大辞典