'phylloxera-resistant' originates as an English compound formed from 'phylloxera' + 'resistant', meaning 'resistant to the insect called phylloxera'.

'phylloxera' comes from New Latin 'Phylloxera', itself formed from Greek elements such as 'phyll-' (from 'phyllon', 'leaf') used in names for leaf-affecting insects; 'resistant' comes from Latin 'resistere' ('to stand back/against'), passed into Old French and Middle English before becoming 'resistant' in modern English.

Initially the parts referred separately to the insect name ('phylloxera') and the Latin notion 'to stand against' ('resistere'); combined in modern English the compound specifically means 'able to withstand attack by phylloxera'.