JLPT4 G3 S8 F38
A depiction of brushwood/firewood piled on a stove. However, 者 was borrowed for use as a demonstrative pronoun, later evolving in meaning to the sense of "the one who does this" → *person*. The present form of 者 and certain derivative characters of 者 eliminate a diagonal stroke above 日, such as is retained for example in 堵, 屠 or 奢.
[Full Kanji Etymology List]