dress corpse for burial
殮 centers on preparing a body for burial, specifically dressing the corpse. It is a specialized funerary kanji with no common abstract extensions.
殮 combines 歹 (death, bones) with 僉, which likely contributes the sound and possibly a sense of gathering or arranging, fitting the idea of preparing a corpse.
The left side 歹 suggests death or remains, and the right side 僉 looks like a person gathering things. Picture someone carefully arranging funeral garments on a body.
For レン, imagine a solemn funeral where a wreath (レン sounds like 'wreath' with a Japanese accent) is placed on the dressed corpse: wreath -> レン.