ガン, ねが.う, ねがい, ら
petition, request, vow, wish, hope
JLPT3 G4 S19 F894
As per 原# (round) + 頁 head → round head. Eventually, 願 came to be associated with the idea of a notion that circulates persistently in the brain (compare 惱 and 慮), leading to the extended meanings *wish*; *desire*; *hope* → *request*; *petition*; *application*.
[Full Kanji Etymology List]