出典:Wiktionary
From Middle English grew, from 古期英語 grēow (first かつ third person past tense of grōwan), from West Germanic *greu, from Northwest Germanic *grerō, from Proto-Germanic *gegrō (first かつ third person past tense of *grōaną), reduplication of *grōaną.
「grew」は動詞「grow」の過去形です