tomb
墦 centers on a tomb or burial mound, specifically an earthen grave marker.
墦 combines 土 (earth) with 番, which likely contributes the sound. The earth radical points to an earthen structure, fitting the tomb meaning.
The left side is earth 土, and the right side 番 looks like a numbered plot. Picture a numbered earthen mound marking a tomb.
For ハン, imagine a hand placing a stone on the earthen tomb: hand -> ハン, and the hand marks the grave.