'biofilm-promoting' is a modern compound formed from the noun 'biofilm' and the present-participial adjective 'promoting'. 'biofilm' itself combines the prefix 'bio-' (from Greek 'bios', meaning 'life') with 'film' (a thin layer or membrane), while 'promoting' comes from the verb 'promote'.

'biofilm' arose in 20th-century scientific English as a compound of 'bio-' + 'film'; 'promote' originates from Latin 'promovere' ('pro-' meaning 'forward' + 'movere' meaning 'to move'), becoming Anglo-Norman/Old French forms and then Middle English 'promoten'/ 'promoven', leading to modern English 'promote' and its participle 'promoting'.

Initially the components meant 'living' + 'thin layer' for 'biofilm' and 'to move forward or advance' for 'promote'; together in modern usage they form a descriptive compound meaning 'encouraging the growth or formation of a biofilm'.