The other meaning of mummy is not horrible! It is just the name given to dead bodies human or animals that have gone through the process of mummification. The archaeologists found a mummy in the tomb. Many mummified remains of animals were found during the dig. The Lady of Dai is known by many as The Diva Mummy.

The process the corpse went through is called mummification. The verb is "to mummify" . The past tense and past participle is mummified, so mummified corpse, which is a bit of a mouthful, so is shortened to mummy. Plural mummies.

In American English, we use "mommy". British English uses "mum" or "mummy". Coincidentally, "mummy" has another meaning.

It's a fluke of language borrowing ... "mummy" referring to preserved dead bodies comes from Persian through Arabic (I believe it comes from a word meaning "wax" in Persian) therefore its relationship to the diminutive "mummy" from "mother" is only a coincidence.