YOU SAID:
ellie is a pain in the buttox
INTO JAPANESE
エリーはお尻の痛みである
BACK INTO ENGLISH
Ellie has a pain in her buttocks.
INTO JAPANESE
エリーはお尻が痛い。
BACK INTO ENGLISH
Ellie's buttocks hurt.
INTO JAPANESE
エリーのお尻が痛い。
BACK INTO ENGLISH
Ellie's buttocks hurt.
That didn't even make that much sense in English.