mummy

In the sense of an embalmed body, mummy traces through Middle English mummie and Anglo-Norman mumie back to Medieval Latin mumia, from Arabic mūmiyāʔ, from Persian mumyâ, ultimately from mum, meaning 'wax.' In the sense of mother, it instead comes from mum plus the diminutive suffix -y.

The embalming sense arrived in English already carrying centuries of borrowing across Latin, Arabic, and Persian, tied to the waxy substances used in preservation. The mother sense took a completely separate path, built directly in English from a child's simple sound for mum.

The 'mother' sense of mummy is closely tied to mom and mommy, both rooted in mother. The 'preserved body' sense is a doublet of mumijo, meaning the two words descend from the same source but arrived in English by different routes.