畳
たたみ · tatami · JLPT N4 · counter
tatami mat (Japanese straw mat)
🎋 tatami = from tatamu, to fold: the mat you fold up and stack
畳 comes from the verb 畳む (tatamu), to fold. Early tatami were thin mats folded or piled away when not in use. The kanji is 田 (field) over a stacking element, so think layers of straw piled up.