autographs (brushwork) of a departed person; posthumous calligraphy
Refers to calligraphy or brushwork left behind by someone who has passed away, often valued as a memento.
This hanging scroll is my grandfather's posthumous calligraphy.
展覧会では著名な作家の遺墨が展示されていた。
At the exhibition, posthumous calligraphy by famous writers was on display.
Compound of 遺 (い, 'left behind') and 墨 (ぼく, 'ink'), referring to ink traces left by a deceased person.