'litter-friendly' originates from modern English by combining the noun 'litter' and the adjective 'friendly'. 'Litter' in English comes via Old French 'litiere' (originally meaning 'bedding' or 'a bed for carrying') and later developed senses including 'scattered refuse'; 'friendly' comes from Old English 'freondlic' meaning 'in a friendly manner'.

'litter' came into English via Old French 'litiere' (related to bed/bedding) and its meaning broadened over time to include scattered refuse; 'friendly' developed from Old English 'freondlic' to the modern adjective 'friendly'. The compound 'litter-friendly' is a modern coinage formed by combining these two words to describe compatibility with or tolerance of litter.

Individually, 'litter' originally referred to bedding and then came to include scattered refuse; 'friendly' originally meant 'like a friend' and broadened to mean 'suitable for' or 'not harmful to'. Together as 'litter-friendly' the compound now means either 'compatible with litter' or 'tolerant/permissive of litter', depending on context.