IPA: //huːmˈsoʊvər//
KK: /huːmˈsoʊvər/
A pronoun used to refer to any person or people, especially in a formal context, often as the object of a verb or preposition.
Whomsoever you choose to invite will be welcome at the party.
Whomsoever is formed from "whom" (from Old English "hwam", meaning to whom) and "soever" (from Old English "swa" meaning so or in this way, combined with "ever" meaning at any time). The word refers to any person to whom something applies, emphasizing inclusivity.
Think of 'whom' as referring to 'to whom' and 'soever' as meaning 'in any way' — together, they help you remember that 'whomsoever' refers to any person in any situation.