IPA: /ˈhuːzˌɛvər/
KK: /ˈhuːzˌɛvər/
Referring to the person or people that something belongs to or is associated with, used in a similar way to 'whoever'.
Whosever book this is, please return it to the library.
'whose' (from Old English 'hwose', meaning of whom) and 'ever' (from Old English 'æfre', meaning at any time). The word 'whosever' combines these parts to mean belonging to or associated with any person at any time.
Think of 'whose' meaning belonging to someone and 'ever' meaning at any time — together, they help you remember that 'whosever' refers to anyone's possession or association.