'libido-decreasing' is a modern English compound formed from 'libido' + the present-participial form 'decreasing' of the verb 'decrease'. 'Libido' comes from Latin 'libido' meaning 'desire', and 'decrease' is from English 'decrease' (see below).

'libido' originates from Latin 'libido' (meaning 'desire, lust') and entered English via scholarly/medical usage in the 17th–19th centuries; 'decrease' comes from Old French and Latin 'decrescere' ('de-' + 'crescere' = 'to grow'), passing into Middle English as 'decrease' and becoming the modern verb. The compound itself is a recent English formation combining these elements.

Initially, 'libido' meant 'strong desire or lust' and 'decrease' meant 'to become less'; combined in modern usage the compound describes something that causes a reduction in sexual desire ('reduces libido').