The word 'improperly-delivered' is a compound formed from 'improperly' (from 'improper' + '-ly') and 'delivered' (past participle of 'deliver'). 'Improper' comes from Latin 'improprius' meaning 'not proper', and 'deliver' comes from Latin 'deliberare' meaning 'to set free'.

'Improperly' and 'delivered' were combined in modern English to describe something that was delivered in an improper way. The use of hyphenated adjectives is common in English to specify the manner of an action.

Initially, 'improperly-delivered' simply described something delivered in an improper way, and this meaning has remained consistent.