What does "'emselves" mean?

Themselves (in unstressed position following a consonant).

What is a synonym for "'emselves"?

Common synonyms include: themselves.

/əmˈsɛlvz/ pron, slang

pron, slang ·Uncommon ·College level

Pronoun

From earlier hemselves (compare 'em), from Middle English hemself, from Old English him selfum, equivalent to 'em + -selves.