'no pets allowed' originates from Modern English, formed by combining 'no' (a native English negator), 'pet' (a word for a domestic animal or a pampered animal), and 'allow' (to permit).

'no pets allowed' developed as a concise negative notice from longer formulations such as 'pets are not allowed' or 'no pets to be admitted' and became common on signs and notices in the 19th–20th century.

Initially it simply stated a prohibition ('pets are not allowed'); it has remained essentially the same in meaning and is now a fixed short notice used on signs and in rules.